diff --git a/lib/ably/modules/ably.rb b/lib/ably/modules/ably.rb
index 0cb5ef9a..0c277617 100644
--- a/lib/ably/modules/ably.rb
+++ b/lib/ably/modules/ably.rb
@@ -11,12 +11,12 @@ module Ably
   FALLBACK_DOMAIN = 'ably-realtime.com'.freeze
   FALLBACK_IDS = %w(a b c d e).freeze
 
-  # Default production fallbacks a.ably-realtime.com ... e.ably-realtime.com
-  FALLBACK_HOSTS = FALLBACK_IDS.map { |host| "#{host}.#{FALLBACK_DOMAIN}".freeze }.freeze
+  # Default production fallbacks main.a.fallback.ably-realtime.com ... main.e.fallback.ably-realtime.com
+  FALLBACK_HOSTS = FALLBACK_IDS.map { |host| "main.#{host}.fallback.#{FALLBACK_DOMAIN}".freeze }.freeze
 
-  # Custom environment default fallbacks {ENV}-a-fallback.ably-realtime.com ... {ENV}-a-fallback.ably-realtime.com
+  # Custom environment default fallbacks {ENV}.a.fallback.ably-realtime.com ... {ENV}.e.fallback.ably-realtime.com
   CUSTOM_ENVIRONMENT_FALLBACKS_SUFFIXES = FALLBACK_IDS.map do |host|
-    "-#{host}-fallback.#{FALLBACK_DOMAIN}".freeze
+    ".#{host}.fallback.#{FALLBACK_DOMAIN}".freeze
   end.freeze
 
   INTERNET_CHECK = {
diff --git a/lib/ably/realtime/client.rb b/lib/ably/realtime/client.rb
index b35aaa94..4b498be7 100644
--- a/lib/ably/realtime/client.rb
+++ b/lib/ably/realtime/client.rb
@@ -73,7 +73,7 @@ class Client
       def_delegators :auth, :client_id, :auth_options
       def_delegators :@rest_client, :encoders
       def_delegators :@rest_client, :use_tls?, :protocol, :protocol_binary?
-      def_delegators :@rest_client, :environment, :custom_host, :custom_port, :custom_tls_port
+      def_delegators :@rest_client, :endpoint, :custom_host, :custom_port, :custom_tls_port
       def_delegators :@rest_client, :log_level
       def_delegators :@rest_client, :options
 
@@ -289,10 +289,24 @@ def publish(channel_name, name, data = nil, attributes = {}, &success_block)
         end
       end
 
-      # @!attribute [r] endpoint
+      # @!attribute [r] hostname
+      # @return [String] The primary hostname to connect to Ably
+      def hostname
+        if endpoint.include?('.') || endpoint.include?('::') || endpoint == 'localhost'
+          return endpoint
+        end
+
+        if endpoint.start_with?('nonprod:')
+          "#{endpoint.gsub('nonprod:', '')}.realtime.#{root_domain}"
+        else
+          "#{endpoint}.realtime.#{root_domain}"
+        end
+      end
+
+      # @!attribute [r] uri
       # @return [URI::Generic] Default Ably Realtime endpoint used for all requests
-      def endpoint
-        endpoint_for_host(custom_realtime_host || [environment, DOMAIN].compact.join('-'))
+      def uri
+        uri_for_host(custom_realtime_host || hostname)
       end
 
       # (see Ably::Rest::Client#register_encoder)
@@ -341,7 +355,8 @@ def device
       end
 
       private
-      def endpoint_for_host(host)
+
+      def uri_for_host(host)
         port = if use_tls?
           custom_tls_port
         else
diff --git a/lib/ably/realtime/connection.rb b/lib/ably/realtime/connection.rb
index 6295ef09..82ddb599 100644
--- a/lib/ably/realtime/connection.rb
+++ b/lib/ably/realtime/connection.rb
@@ -173,7 +173,7 @@ def initialize(client, options)
         @state         = STATE(state_machine.current_state)
         @manager       = ConnectionManager.new(self)
 
-        @current_host = client.endpoint.host
+        @current_host = client.uri.host
 
         reset_client_msg_serial
       end
@@ -396,12 +396,12 @@ def determine_host
             @current_host = if internet_is_up_result
               client.fallback_endpoint.host
             else
-              client.endpoint.host
+              client.uri.host
             end
             yield current_host
           end
         else
-          @current_host = client.endpoint.host
+          @current_host = client.uri.host
           yield current_host
         end
       end
@@ -496,8 +496,8 @@ def create_websocket_transport
                 end
               end
 
-              url = URI(client.endpoint).tap do |endpoint|
-                endpoint.query = URI.encode_www_form(url_params)
+              url = URI(client.uri).tap do |uri|
+                uri.query = URI.encode_www_form(url_params)
               end
 
               determine_host do |host|
diff --git a/lib/ably/rest/client.rb b/lib/ably/rest/client.rb
index 3dbda2df..d32ad69e 100644
--- a/lib/ably/rest/client.rb
+++ b/lib/ably/rest/client.rb
@@ -43,9 +43,9 @@ class Client
 
       def_delegators :auth, :client_id, :auth_options
 
-      # Custom environment to use such as 'sandbox' when testing the client library against an alternate Ably environment
+      # The hostname used to connect to Ably
       # @return [String]
-      attr_reader :environment
+      attr_reader :endpoint
 
       # The protocol configured for this client, either binary `:msgpack` or text based `:json`
       # @return [Symbol]
@@ -135,7 +135,8 @@ class Client
       # @option options [String]                  :token               Token string or {Models::TokenDetails} used to authenticate requests
       # @option options [String]                  :token_details       {Models::TokenDetails} used to authenticate requests
       # @option options [Boolean]                 :use_token_auth      Will force Basic Auth if set to false, and Token auth if set to true
-      # @option options [String]                  :environment         Specify 'sandbox' when testing the client library against an alternate Ably environment
+      # @option options [String]                  :endpoint            Specify a routing policy or fully-qualified domain name to connect to Ably
+      # @option options [String]                  :environment         Specify 'sandbox' when testing the client library against an alternate Ably environment (deprecated)
       # @option options [Symbol]                  :protocol            (:msgpack) Protocol used to communicate with Ably, :json and :msgpack currently supported
       # @option options [Boolean]                 :use_binary_protocol (true) When true will use the MessagePack binary protocol, when false it will use JSON encoding. This option will overide :protocol option
       # @option options [Logger::Severity,Symbol] :log_level           (Logger::WARN) Log level for the standard Logger that outputs to STDOUT. Can be set to :fatal (Logger::FATAL), :error (Logger::ERROR), :warn (Logger::WARN), :info (Logger::INFO), :debug (Logger::DEBUG) or :none
@@ -188,8 +189,6 @@ def initialize(options)
         @agent               = options.delete(:agent) || Ably::AGENT
         @realtime_client     = options.delete(:realtime_client)
         @tls                 = options.delete_with_default(:tls, true)
-        @environment         = options.delete(:environment) # nil is production
-        @environment         = nil if [:production, 'production'].include?(@environment)
         @protocol            = options.delete(:protocol) || :msgpack
         @debug_http          = options.delete(:debug_http)
         @log_level           = options.delete(:log_level) || ::Logger::WARN
@@ -203,9 +202,14 @@ def initialize(options)
         @max_frame_size      = options.delete(:max_frame_size) || MAX_FRAME_SIZE
         @idempotent_rest_publishing = options.delete_with_default(:idempotent_rest_publishing, true)
 
+        @environment         = options.delete(:environment) # nil is production
+        @environment         = nil if [:production, 'production'].include?(@environment)
+        @endpoint            = @environment || options.delete_with_default(:endpoint, 'main')
+
         if options[:fallback_hosts_use_default] && options[:fallback_hosts]
           raise ArgumentError, "fallback_hosts_use_default cannot be set to try when fallback_hosts is also provided"
         end
+
         @fallback_hosts = case
         when options.delete(:fallback_hosts_use_default)
           Ably::FALLBACK_HOSTS
@@ -213,8 +217,12 @@ def initialize(options)
           options_fallback_hosts
         when custom_host || options[:realtime_host] || custom_port || custom_tls_port
           []
-        when environment
-          CUSTOM_ENVIRONMENT_FALLBACKS_SUFFIXES.map { |host| "#{environment}#{host}" }
+        when endpoint
+          if endpoint.start_with?('nonprod:')
+            CUSTOM_ENVIRONMENT_FALLBACKS_SUFFIXES.map { |host| "#{endpoint.gsub('nonprod:', '')}.#{host}" }
+          else
+            CUSTOM_ENVIRONMENT_FALLBACKS_SUFFIXES.map { |host| "#{endpoint}.#{host}" }
+          end
         else
           Ably::FALLBACK_HOSTS
         end
@@ -426,10 +434,24 @@ def push
         @push ||= Push.new(self)
       end
 
-      # @!attribute [r] endpoint
+      # @!attribute [r] hostname
+      # @return [String] The primary hostname to connect to Ably
+      def hostname
+        if endpoint.include?('.') || endpoint.include?('::') || endpoint == 'localhost'
+          return endpoint
+        end
+
+        if endpoint.start_with?('nonprod:')
+          "#{endpoint.gsub('nonprod:', '')}.realtime.#{root_domain}"
+        else
+          "#{endpoint}.realtime.#{root_domain}"
+        end
+      end
+
+      # @!attribute [r] uri
       # @return [URI::Generic] Default Ably REST endpoint used for all requests
-      def endpoint
-        endpoint_for_host(custom_host || [@environment, DOMAIN].compact.join('-'))
+      def uri
+        uri_for_host(custom_host || hostname)
       end
 
       # @!attribute [r] logger
@@ -480,7 +502,7 @@ def connection(options = {})
         if options[:use_fallback]
           fallback_connection
         else
-          @connection ||= Faraday.new(endpoint.to_s, connection_options)
+          @connection ||= Faraday.new(uri.to_s, connection_options)
         end
       end
 
@@ -493,7 +515,7 @@ def connection(options = {})
       # @api private
       def fallback_connection
         unless defined?(@fallback_connections) && @fallback_connections
-          @fallback_connections = fallback_hosts.shuffle.map { |host| Faraday.new(endpoint_for_host(host).to_s, connection_options) }
+          @fallback_connections = fallback_hosts.shuffle.map { |host| Faraday.new(uri_for_host(host).to_s, connection_options) }
         end
         @fallback_index ||= 0
 
@@ -653,7 +675,7 @@ def reauthorize_on_authorization_failure
         end
       end
 
-      def endpoint_for_host(host)
+      def uri_for_host(host)
         port = if use_tls?
           custom_tls_port
         else
@@ -671,6 +693,14 @@ def endpoint_for_host(host)
         URI::Generic.build(options)
       end
 
+      def root_domain
+        if endpoint.start_with?('nonprod:')
+          'ably-nonprod.net'
+        else
+          'ably.net'
+        end
+      end
+
       # Return a Hash of connection options to initiate the Faraday::Connection with
       #
       # @return [Hash]
diff --git a/spec/acceptance/realtime/client_spec.rb b/spec/acceptance/realtime/client_spec.rb
index b392d118..ce26dd30 100644
--- a/spec/acceptance/realtime/client_spec.rb
+++ b/spec/acceptance/realtime/client_spec.rb
@@ -234,7 +234,7 @@
     context '#request (#RSC19*)' do
       let(:client_options) { default_options.merge(key: api_key) }
       let(:device_id) { random_str }
-      let(:endpoint) { subject.rest_client.endpoint }
+      let(:uri) { subject.rest_client.uri }
 
       context 'get' do
         it 'returns an HttpPaginatedResponse object' do
@@ -287,7 +287,7 @@
 
       context 'post', :webmock do
         before do
-          stub_request(:delete, "#{endpoint}/push/deviceRegistrations/#{device_id}/resetUpdateToken").
+          stub_request(:delete, "#{uri}/push/deviceRegistrations/#{device_id}/resetUpdateToken").
             to_return(status: 200, body: '{}', headers: { 'Content-Type' => 'application/json' })
         end
 
@@ -301,7 +301,7 @@
 
       context 'delete', :webmock do
         before do
-          stub_request(:delete, "#{endpoint}/push/channelSubscriptions?deviceId=#{device_id}").
+          stub_request(:delete, "#{uri}/push/channelSubscriptions?deviceId=#{device_id}").
             to_return(status: 200, body: '{}', headers: { 'Content-Type' => 'application/json' })
         end
 
@@ -317,7 +317,7 @@
         let(:body_params) { { 'metadata' => { 'key' => 'value' } } }
 
         before do
-          stub_request(:patch, "#{endpoint}/push/deviceRegistrations/#{device_id}")
+          stub_request(:patch, "#{uri}/push/deviceRegistrations/#{device_id}")
             .with(body: serialize_body(body_params, protocol))
             .to_return(status: 200, body: '{}', headers: { 'Content-Type' => 'application/json' })
         end
@@ -341,7 +341,7 @@
         end
 
         before do
-          stub_request(:put, "#{endpoint}/push/deviceRegistrations/#{device_id}")
+          stub_request(:put, "#{uri}/push/deviceRegistrations/#{device_id}")
             .with(body: serialize_body(body_params, protocol))
             .to_return(status: 200, body: '{}', headers: { 'Content-Type' => 'application/json' })
         end
diff --git a/spec/acceptance/realtime/message_spec.rb b/spec/acceptance/realtime/message_spec.rb
index b218a8e1..63c8aa35 100644
--- a/spec/acceptance/realtime/message_spec.rb
+++ b/spec/acceptance/realtime/message_spec.rb
@@ -775,7 +775,7 @@ def publish_and_check_extras(extras)
                 EventMachine.add_timer(0.0001) do
                   connection.transition_state_machine :suspended
                   stub_const 'Ably::FALLBACK_HOSTS', []
-                  allow(client).to receive(:endpoint).and_return(URI::Generic.build(scheme: 'wss', host: 'does.not.exist.com'))
+                  allow(client).to receive(:uri).and_return(URI::Generic.build(scheme: 'wss', host: 'does.not.exist.com'))
                 end
               end
             end
diff --git a/spec/acceptance/realtime/push_admin_spec.rb b/spec/acceptance/realtime/push_admin_spec.rb
index e9dfba92..1be57968 100644
--- a/spec/acceptance/realtime/push_admin_spec.rb
+++ b/spec/acceptance/realtime/push_admin_spec.rb
@@ -102,7 +102,7 @@
         end
 
         let!(:publish_stub) do
-          stub_request(:post, "#{client.rest_client.endpoint}/push/publish").
+          stub_request(:post, "#{client.rest_client.uri}/push/publish").
             with do |request|
               expect(deserialize_body(request.body, protocol)['recipient']['camelCase']['secondLevelCamelCase']).to eql('val')
               expect(deserialize_body(request.body, protocol)['recipient']).to_not have_key('camel_case')
@@ -135,7 +135,7 @@
             'transportType' => 'ablyChannel',
             'channel' => channel,
             'ablyKey' => api_key,
-            'ablyUrl' => client.rest_client.endpoint.to_s
+            'ablyUrl' => client.rest_client.uri.to_s
           }
         end
         let(:notification_payload) do
diff --git a/spec/acceptance/rest/auth_spec.rb b/spec/acceptance/rest/auth_spec.rb
index ef07af9f..6b34e8f1 100644
--- a/spec/acceptance/rest/auth_spec.rb
+++ b/spec/acceptance/rest/auth_spec.rb
@@ -61,7 +61,7 @@ def request_body_includes(request, protocol, key, val)
       end
 
       it 'creates a TokenRequest automatically and sends it to Ably to obtain a token', webmock: true do
-        token_request_stub = stub_request(:post, "#{client.endpoint}/keys/#{key_name}/requestToken").
+        token_request_stub = stub_request(:post, "#{client.uri}/keys/#{key_name}/requestToken").
           to_return(status: 201, body: serialize_body({}, protocol), headers: { 'Content-Type' => content_type })
         expect(auth).to receive(:create_token_request).and_call_original
         auth.request_token
@@ -90,7 +90,7 @@ def coerce_if_time_value(field_name, value, params = {})
 
           let(:token_response) { {} }
           let!(:request_token_stub) do
-            stub_request(:post, "#{client.endpoint}/keys/#{key_name}/requestToken").
+            stub_request(:post, "#{client.uri}/keys/#{key_name}/requestToken").
               with do |request|
                 request_body_includes(request, protocol, token_param, coerce_if_time_value(token_param, random, multiply: 1000))
               end.to_return(
@@ -121,7 +121,7 @@ def coerce_if_time_value(field_name, value, params = {})
 
         let(:token_response) { {} }
         let!(:request_token_stub) do
-          stub_request(:post, "#{client.endpoint}/keys/#{key_name}/requestToken").
+          stub_request(:post, "#{client.uri}/keys/#{key_name}/requestToken").
             with do |request|
               request_body_includes(request, protocol, 'mac', mac)
             end.to_return(
@@ -151,7 +151,7 @@ def coerce_if_time_value(field_name, value, params = {})
 
         let(:token_response) { {} }
         let!(:request_token_stub) do
-          stub_request(:post, "#{client.endpoint}/keys/#{key_name}/requestToken").
+          stub_request(:post, "#{client.uri}/keys/#{key_name}/requestToken").
             with do |request|
               request_body_includes(request, protocol, 'mac', mac)
             end.to_return(
@@ -293,7 +293,7 @@ def coerce_if_time_value(field_name, value, params = {})
         let(:auth_url_content_type) { 'application/json' }
 
         let!(:request_token_stub) do
-          stub_request(:post, "#{client.endpoint}/keys/#{key_name}/requestToken").
+          stub_request(:post, "#{client.uri}/keys/#{key_name}/requestToken").
             with do |request|
               request_body_includes(request, protocol, 'key_name', key_name)
             end.to_return(
diff --git a/spec/acceptance/rest/base_spec.rb b/spec/acceptance/rest/base_spec.rb
index 0e046458..4a8ff749 100644
--- a/spec/acceptance/rest/base_spec.rb
+++ b/spec/acceptance/rest/base_spec.rb
@@ -14,7 +14,7 @@
     let(:body_value) { [as_since_epoch(now)] }
 
     before do
-      stub_request(:get, "#{client.endpoint}/time").
+      stub_request(:get, "#{client.uri}/time").
         with(:headers => { 'Accept' => mime }).
         to_return(:status => 200, :body => request_body, :headers => { 'Content-Type' => mime })
     end
@@ -87,7 +87,7 @@
         let(:error_response) { '{ "error": { "statusCode": 500, "code": 50000, "message": "Internal error" } }' }
 
         before do
-          (client.fallback_hosts.map { |host| "https://#{host}" } + [client.endpoint]).each do |host|
+          (client.fallback_hosts.map { |host| "https://#{host}" } + [client.uri]).each do |host|
             stub_request(:get, "#{host}/time")
               .to_return(:status => 500, :body => error_response, :headers => { 'Content-Type' => 'application/json' })
           end
@@ -100,7 +100,7 @@
 
       describe '500 server error without a valid JSON response body', :webmock do
         before do
-          (client.fallback_hosts.map { |host| "https://#{host}" } + [client.endpoint]).each do |host|
+          (client.fallback_hosts.map { |host| "https://#{host}" } + [client.uri]).each do |host|
             stub_request(:get, "#{host}/time").
             to_return(:status => 500, :headers => { 'Content-Type' => 'application/json' })
           end
@@ -121,7 +121,7 @@
         @token_requests = 0
         @publish_attempts = 0
 
-        stub_request(:post, "#{client.endpoint}/keys/#{key_name}/requestToken").to_return do
+        stub_request(:post, "#{client.uri}/keys/#{key_name}/requestToken").to_return do
           @token_requests += 1
           {
             :body => public_send("token_#{@token_requests}").merge(expires: (Time.now.to_i + 60) * 1000).to_json,
@@ -129,7 +129,7 @@
           }
         end
 
-        stub_request(:post, "#{client.endpoint}/channels/#{channel}/publish").to_return do
+        stub_request(:post, "#{client.uri}/channels/#{channel}/publish").to_return do
           @publish_attempts += 1
           if [1, 3].include?(@publish_attempts)
             { status: 201, :body => '[]', :headers => { 'Content-Type' => 'application/json' } }
diff --git a/spec/acceptance/rest/channel_spec.rb b/spec/acceptance/rest/channel_spec.rb
index 37a4e174..36d15eab 100644
--- a/spec/acceptance/rest/channel_spec.rb
+++ b/spec/acceptance/rest/channel_spec.rb
@@ -364,12 +364,12 @@
       context 'with a non ASCII channel name' do
         let(:channel_name) { 'foo:¡€≤`☃' }
         let(:channel_name_encoded) { 'foo%3A%C2%A1%E2%82%AC%E2%89%A4%60%E2%98%83' }
-        let(:endpoint) { client.endpoint }
+        let(:uri) { client.uri }
         let(:channel) { client.channels.get(channel_name) }
 
         context 'stubbed', :webmock do
           let!(:get_stub) {
-            stub_request(:post, "#{endpoint}/channels/#{channel_name_encoded}/publish").
+            stub_request(:post, "#{uri}/channels/#{channel_name_encoded}/publish").
               to_return(:body => '{}', :headers => { 'Content-Type' => 'application/json' })
           }
 
@@ -534,8 +534,8 @@
     describe '#history option' do
       let(:channel_name) { "persisted:#{random_str(4)}" }
       let(:channel) { client.channel(channel_name) }
-      let(:endpoint) do
-        client.endpoint
+      let(:uri) do
+        client.uri
       end
       let(:default_history_options) do
           {
@@ -549,7 +549,7 @@
           let!(:history_stub) {
             query_params = default_history_options
             .merge(option => milliseconds).map { |k, v| "#{k}=#{v}" }.join('&')
-            stub_request(:get, "#{endpoint}/channels/#{URI.encode_www_form_component(channel_name)}/messages?#{query_params}").
+            stub_request(:get, "#{uri}/channels/#{URI.encode_www_form_component(channel_name)}/messages?#{query_params}").
               to_return(:body => '{}', :headers => { 'Content-Type' => 'application/json' })
           }
 
diff --git a/spec/acceptance/rest/client_spec.rb b/spec/acceptance/rest/client_spec.rb
index e1619c6e..8d9d38de 100644
--- a/spec/acceptance/rest/client_spec.rb
+++ b/spec/acceptance/rest/client_spec.rb
@@ -301,12 +301,12 @@ def encode64(text)
       context 'configured' do
         let(:client_options) { default_options.merge(key: api_key, environment: 'production') }
 
-        it 'should make connection attempts to a.ably-realtime.com, b.ably-realtime.com, c.ably-realtime.com, d.ably-realtime.com, e.ably-realtime.com (#RSC15a)' do
+        it 'should make connection attempts to main.a.fallback.ably-realtime.com, main.b.fallback.ably-realtime.com, main.c.fallback.ably-realtime.com, main.d.fallback.ably-realtime.com, main.e.fallback.ably-realtime.com (#RSC15a)' do
           hosts = []
           5.times do
             hosts << client.fallback_connection.host
           end
-          expect(hosts).to match_array(%w(a.ably-realtime.com b.ably-realtime.com c.ably-realtime.com d.ably-realtime.com e.ably-realtime.com))
+          expect(hosts).to match_array(%w(main.a.fallback.ably-realtime.com main.b.fallback.ably-realtime.com main.c.fallback.ably-realtime.com main.d.fallback.ably-realtime.com main.e.fallback.ably-realtime.com))
         end
       end
 
@@ -327,12 +327,12 @@ def encode64(text)
         context 'and no custom fallback hosts are provided' do
           let(:client_options) { default_options.merge(environment: 'sandbox', key: api_key) }
 
-          it 'should make connection attempts to sandbox-a-fallback.ably-realtime.com, sandbox-b-fallback.ably-realtime.com, sandbox-c-fallback.ably-realtime.com, sandbox-d-fallback.ably-realtime.com, sandbox-e-fallback.ably-realtime.com (#RSC15a)' do
+          it 'should make connection attempts to sandbox.a.fallback.ably-realtime.com, sandbox.b.fallback.ably-realtime.com, sandbox.c.fallback.ably-realtime.com, sandbox.d.fallback.ably-realtime.com, sandbox.e.fallback.ably-realtime.com (#RSC15a)' do
             hosts = []
             5.times do
               hosts << client.fallback_connection.host
             end
-            expect(hosts).to match_array(%w(a b c d e).map { |id| "sandbox-#{id}-fallback.ably-realtime.com" })
+            expect(hosts).to match_array(%w(a b c d e).map { |id| "sandbox.#{id}.fallback.ably-realtime.com" })
           end
         end
       end
@@ -554,8 +554,8 @@ def encode64(text)
         end
 
         context 'using a local web-server', webmock: false do
-          let(:primary_host) { 'local-rest.ably.io' }
-          let(:fallbacks) { ['local.ably.io', 'localhost'] }
+          let(:primary_host) { 'local.realtime.ably.net' }
+          let(:fallbacks) { ['local.ably.net', 'localhost'] }
           let(:port) { rand(10000) + 2000 }
           let(:channel_name) { 'foo' }
           let(:request_timeout) { 3 }
@@ -838,7 +838,7 @@ def encode64(text)
 
       context 'when environment is not production and server returns a 50x error' do
         let(:env)                { 'custom-env' }
-        let(:default_fallbacks)  { %w(a b c d e).map { |id| "#{env}-#{id}-fallback.ably-realtime.com" } }
+        let(:default_fallbacks)  { %w(a b c d e).map { |id| "#{env}.#{id}.fallback.ably-realtime.com" } }
         let(:custom_hosts)       { %w(A.foo.com B.foo.com) }
         let(:max_retry_count)    { 2 }
         let(:max_retry_duration) { 0.5 }
@@ -1086,7 +1086,7 @@ def encode64(text)
           let(:client_options) { default_options.merge(key: api_key, agent: agent) }
 
           let!(:publish_message_stub) do
-            stub_request(:post, "#{client.endpoint}/channels/foo/publish").
+            stub_request(:post, "#{client.uri}/channels/foo/publish").
               with(headers: {
                 'X-Ably-Version' => Ably::PROTOCOL_VERSION,
                 'Ably-Agent' => agent || Ably::AGENT
@@ -1113,7 +1113,7 @@ def encode64(text)
     context '#request (#RSC19*, #TO3l9)' do
       let(:client_options) { default_options.merge(key: api_key) }
       let(:device_id) { random_str }
-      let(:endpoint) { client.endpoint }
+      let(:uri) { client.uri }
 
       context 'get' do
         it 'returns an HttpPaginatedResponse object' do
@@ -1156,7 +1156,7 @@ def encode64(text)
 
       context 'post', :webmock do
         before do
-          stub_request(:delete, "#{endpoint}/push/deviceRegistrations/#{device_id}/resetUpdateToken").
+          stub_request(:delete, "#{uri}/push/deviceRegistrations/#{device_id}/resetUpdateToken").
             to_return(status: 200, body: '{}', headers: { 'Content-Type' => 'application/json' })
         end
 
@@ -1168,14 +1168,14 @@ def encode64(text)
 
         it 'raises an exception once body size in bytes exceeded' do
           expect {
-            client.request(:post, endpoint, {}, { content: 'x' * Ably::Rest::Client::MAX_FRAME_SIZE })
+            client.request(:post, uri, {}, { content: 'x' * Ably::Rest::Client::MAX_FRAME_SIZE })
           }.to raise_error(Ably::Exceptions::MaxFrameSizeExceeded)
         end
       end
 
       context 'delete', :webmock do
         before do
-          stub_request(:delete, "#{endpoint}/push/channelSubscriptions?deviceId=#{device_id}").
+          stub_request(:delete, "#{uri}/push/channelSubscriptions?deviceId=#{device_id}").
             to_return(status: 200, body: '{}', headers: { 'Content-Type' => 'application/json' })
         end
 
@@ -1190,7 +1190,7 @@ def encode64(text)
         let(:body_params) { { 'metadata' => { 'key' => 'value' } } }
 
         before do
-          stub_request(:patch, "#{endpoint}/push/deviceRegistrations/#{device_id}")
+          stub_request(:patch, "#{uri}/push/deviceRegistrations/#{device_id}")
             .with(body: serialize_body(body_params, protocol))
             .to_return(status: 200, body: '{}', headers: { 'Content-Type' => 'application/json' })
         end
@@ -1203,7 +1203,7 @@ def encode64(text)
 
         it 'raises an exception once body size in bytes exceeded' do
           expect {
-            client.request(:patch, endpoint, {}, { content: 'x' * Ably::Rest::Client::MAX_FRAME_SIZE })
+            client.request(:patch, uri, {}, { content: 'x' * Ably::Rest::Client::MAX_FRAME_SIZE })
           }.to raise_error(Ably::Exceptions::MaxFrameSizeExceeded)
         end
       end
@@ -1219,7 +1219,7 @@ def encode64(text)
         end
 
         before do
-          stub_request(:put, "#{endpoint}/push/deviceRegistrations/#{device_id}")
+          stub_request(:put, "#{uri}/push/deviceRegistrations/#{device_id}")
             .with(body: serialize_body(body_params, protocol))
             .to_return(status: 200, body: '{}', headers: { 'Content-Type' => 'application/json' })
         end
@@ -1232,7 +1232,7 @@ def encode64(text)
 
         it 'raises an exception once body size in bytes exceeded' do
           expect {
-            client.request(:put, endpoint, {}, { content: 'x' * Ably::Rest::Client::MAX_FRAME_SIZE })
+            client.request(:put, uri, {}, { content: 'x' * Ably::Rest::Client::MAX_FRAME_SIZE })
           }.to raise_error(Ably::Exceptions::MaxFrameSizeExceeded)
         end
       end
@@ -1246,7 +1246,7 @@ def encode64(text)
 
           before do
             @request_id = nil
-            stub_request(:get, Addressable::Template.new("#{client.endpoint}/time{?request_id}")).with do |request|
+            stub_request(:get, Addressable::Template.new("#{client.uri}/time{?request_id}")).with do |request|
               @request_id = request.uri.query_values['request_id']
             end.to_return do
               raise Faraday::TimeoutError.new('timeout error message')
@@ -1268,7 +1268,7 @@ def encode64(text)
 
           context 'with mocks to inspect the params', :webmock do
             before do
-              stub_request(:post, Addressable::Template.new("#{client.endpoint}/channels/#{channel_name}/publish{?request_id}")).
+              stub_request(:post, Addressable::Template.new("#{client.uri}/channels/#{channel_name}/publish{?request_id}")).
                 with do |request|
                   @request_id = request.uri.query_values['request_id']
                 end.to_return(:status => 200, :body => [], :headers => { 'Content-Type' => 'application/json' })
@@ -1312,7 +1312,7 @@ def encode64(text)
 
           before do
             @request_id = nil
-            hosts = Ably::FALLBACK_HOSTS + ['rest.ably.io']
+            hosts = Ably::FALLBACK_HOSTS + ['main.realtime.ably.net']
             hosts.each do |host|
               stub_request(:get, Addressable::Template.new("https://#{host.downcase}/time{?request_id}")).with do |request|
                 @request_id = request.uri.query_values['request_id']
diff --git a/spec/acceptance/rest/presence_spec.rb b/spec/acceptance/rest/presence_spec.rb
index b0c61c8e..bd76f460 100644
--- a/spec/acceptance/rest/presence_spec.rb
+++ b/spec/acceptance/rest/presence_spec.rb
@@ -68,12 +68,12 @@
               limit: 100
             }
           end
-          let(:endpoint) do
-            client.endpoint
+          let(:uri) do
+            client.uri
           end
           let!(:get_stub) {
             query_params = query_options.map { |k, v| "#{k}=#{v}" }.join('&')
-            stub_request(:get, "#{endpoint}/channels/#{URI.encode_www_form_component(channel_name)}/presence?#{query_params}").
+            stub_request(:get, "#{uri}/channels/#{URI.encode_www_form_component(channel_name)}/presence?#{query_params}").
               to_return(:body => '{}', :headers => { 'Content-Type' => 'application/json' })
           }
           let(:channel_name) { random_str }
@@ -115,12 +115,12 @@
         context 'with a non ASCII channel name' do
           let(:channel_name) { 'foo:¡€≤`☃' }
           let(:channel_name_encoded) { 'foo%3A%C2%A1%E2%82%AC%E2%89%A4%60%E2%98%83' }
-          let(:endpoint) { client.endpoint }
+          let(:uri) { client.uri }
           let(:channel) { client.channels.get(channel_name) }
 
           context 'stubbed', :webmock do
             let!(:get_stub) {
-              stub_request(:get, "#{endpoint}/channels/#{channel_name_encoded}/presence?limit=100").
+              stub_request(:get, "#{uri}/channels/#{channel_name_encoded}/presence?limit=100").
                 to_return(:body => '{}', :headers => { 'Content-Type' => 'application/json' })
             }
 
@@ -197,8 +197,8 @@
         let(:presence) { client.channel(channel_name).presence }
         let(:user) { 'appid.keyuid' }
         let(:secret) { random_str(8) }
-        let(:endpoint) do
-          client.endpoint
+        let(:uri) do
+          client.uri
         end
         let(:client) do
           Ably::Rest::Client.new(key: "#{user}:#{secret}")
@@ -213,7 +213,7 @@
         context 'limit options', :webmock do
           let!(:history_stub) {
             query_params = history_options.map { |k, v| "#{k}=#{v}" }.join('&')
-            stub_request(:get, "#{endpoint}/channels/#{URI.encode_www_form_component(channel_name)}/presence/history?#{query_params}").
+            stub_request(:get, "#{uri}/channels/#{URI.encode_www_form_component(channel_name)}/presence/history?#{query_params}").
               to_return(:body => '{}', :headers => { 'Content-Type' => 'application/json' })
           }
 
@@ -253,7 +253,7 @@
               }
               let!(:history_stub) {
                 query_params = history_options.map { |k, v| "#{k}=#{v}" }.join('&')
-                stub_request(:get, "#{endpoint}/channels/#{URI.encode_www_form_component(channel_name)}/presence/history?#{query_params}").
+                stub_request(:get, "#{uri}/channels/#{URI.encode_www_form_component(channel_name)}/presence/history?#{query_params}").
                   to_return(:body => '{}', :headers => { 'Content-Type' => 'application/json' })
               }
 
@@ -322,8 +322,8 @@ def message(client_id, messages)
     describe 'decoding permutations using mocked #history', :webmock do
       let(:user) { 'appid.keyuid' }
       let(:secret) { random_str(8) }
-      let(:endpoint) do
-        client.endpoint
+      let(:uri) do
+        client.uri
       end
       let(:client) do
         Ably::Rest::Client.new(client_options.merge(key: "#{user}:#{secret}"))
@@ -357,7 +357,7 @@ def message(client_id, messages)
 
         context '#get' do
           let!(:get_stub)   {
-            stub_request(:get, "#{endpoint}/channels/#{URI.encode_www_form_component(channel_name)}/presence?limit=100").
+            stub_request(:get, "#{uri}/channels/#{URI.encode_www_form_component(channel_name)}/presence?limit=100").
               to_return(:body => serialized_encoded_message, :headers => { 'Content-Type' => content_type })
           }
 
@@ -374,7 +374,7 @@ def message(client_id, messages)
 
         context '#history' do
           let!(:history_stub)   {
-            stub_request(:get, "#{endpoint}/channels/#{URI.encode_www_form_component(channel_name)}/presence/history?direction=backwards&limit=100").
+            stub_request(:get, "#{uri}/channels/#{URI.encode_www_form_component(channel_name)}/presence/history?direction=backwards&limit=100").
               to_return(:body => serialized_encoded_message, :headers => { 'Content-Type' => content_type })
           }
 
@@ -404,7 +404,7 @@ def message(client_id, messages)
         context '#get' do
           let(:client_options) { default_options.merge(log_level: :fatal) }
           let!(:get_stub)   {
-            stub_request(:get, "#{endpoint}/channels/#{URI.encode_www_form_component(channel_name)}/presence?limit=100").
+            stub_request(:get, "#{uri}/channels/#{URI.encode_www_form_component(channel_name)}/presence?limit=100").
               to_return(:body => serialized_encoded_message_with_invalid_encoding, :headers => { 'Content-Type' => content_type })
           }
           let(:presence_message) { presence.get.items.first }
@@ -428,7 +428,7 @@ def message(client_id, messages)
         context '#history' do
           let(:client_options) { default_options.merge(log_level: :fatal) }
           let!(:history_stub)   {
-            stub_request(:get, "#{endpoint}/channels/#{URI.encode_www_form_component(channel_name)}/presence/history?direction=backwards&limit=100").
+            stub_request(:get, "#{uri}/channels/#{URI.encode_www_form_component(channel_name)}/presence/history?direction=backwards&limit=100").
               to_return(:body => serialized_encoded_message_with_invalid_encoding, :headers => { 'Content-Type' => content_type })
           }
           let(:presence_message) { presence.history.items.first }
diff --git a/spec/acceptance/rest/push_admin_spec.rb b/spec/acceptance/rest/push_admin_spec.rb
index a5e1433f..36824fa4 100644
--- a/spec/acceptance/rest/push_admin_spec.rb
+++ b/spec/acceptance/rest/push_admin_spec.rb
@@ -90,7 +90,7 @@
         end
 
         let!(:publish_stub) do
-          stub_request(:post, "#{client.endpoint}/push/publish").
+          stub_request(:post, "#{client.uri}/push/publish").
             with do |request|
               expect(deserialize_body(request.body, protocol)['recipient']['camelCase']['secondLevelCamelCase']).to eql('val')
               expect(deserialize_body(request.body, protocol)['recipient']).to_not have_key('camel_case')
@@ -119,7 +119,7 @@
             'transportType' => 'ablyChannel',
             'channel' => channel,
             'ablyKey' => api_key,
-            'ablyUrl' => client.endpoint.to_s
+            'ablyUrl' => client.uri.to_s
           }
         end
         let(:notification_payload) do
diff --git a/spec/shared/client_initializer_behaviour.rb b/spec/shared/client_initializer_behaviour.rb
index 84ff2df4..9d0d66a8 100644
--- a/spec/shared/client_initializer_behaviour.rb
+++ b/spec/shared/client_initializer_behaviour.rb
@@ -1,14 +1,6 @@
 # encoding: utf-8
 
 shared_examples 'a client initializer' do
-  def subdomain
-    if rest?
-      'rest'
-    else
-      'realtime'
-    end
-  end
-
   def protocol
     if rest?
       'http'
@@ -154,38 +146,38 @@ def rest?
       end
     end
 
-    context 'endpoint' do
+    context 'uri' do
       before do
         allow_any_instance_of(subject.class).to receive(:auto_connect).and_return(false)
       end
 
       it 'defaults to production' do
-        expect(subject.endpoint.to_s).to eql("#{protocol}s://#{subdomain}.ably.io")
+        expect(subject.uri.to_s).to eql("#{protocol}s://main.realtime.ably.net")
       end
 
       context 'with environment option' do
         let(:client_options) { default_options.merge(environment: 'sandbox', auto_connect: false) }
 
-        it 'uses an alternate endpoint' do
-          expect(subject.endpoint.to_s).to eql("#{protocol}s://sandbox-#{subdomain}.ably.io")
+        it 'uses an alternate uri' do
+          expect(subject.uri.to_s).to eql("#{protocol}s://sandbox.realtime.ably.net")
         end
       end
 
       context 'with rest_host option' do
         let(:client_options) { default_options.merge(rest_host: 'custom-rest.host.com', auto_connect: false) }
 
-        it 'uses an alternate endpoint for REST clients' do
+        it 'uses an alternate uri for REST clients' do
           skip 'does not apply as testing a Realtime client' unless rest?
-          expect(subject.endpoint.to_s).to eql("#{protocol}s://custom-rest.host.com")
+          expect(subject.uri.to_s).to eql("#{protocol}s://custom-rest.host.com")
         end
       end
 
       context 'with realtime_host option' do
         let(:client_options) { default_options.merge(realtime_host: 'custom-realtime.host.com', auto_connect: false) }
 
-        it 'uses an alternate endpoint for Realtime clients' do
+        it 'uses an alternate uri for Realtime clients' do
           skip 'does not apply as testing a REST client' if rest?
-          expect(subject.endpoint.to_s).to eql("#{protocol}s://custom-realtime.host.com")
+          expect(subject.uri.to_s).to eql("#{protocol}s://custom-realtime.host.com")
         end
       end
 
@@ -193,7 +185,7 @@ def rest?
         let(:client_options) { default_options.merge(port: 999, tls: false, auto_connect: false) }
 
         it 'uses the custom port for non-TLS requests' do
-          expect(subject.endpoint.to_s).to include(":999")
+          expect(subject.uri.to_s).to include(":999")
         end
       end
 
@@ -201,7 +193,7 @@ def rest?
         let(:client_options) { default_options.merge(tls_port: 666, tls: true, auto_connect: false) }
 
         it 'uses the custom port for TLS requests' do
-          expect(subject.endpoint.to_s).to include(":666")
+          expect(subject.uri.to_s).to include(":666")
         end
       end
     end
@@ -219,7 +211,7 @@ def rest?
         end
 
         it 'uses HTTP' do
-          expect(subject.endpoint.to_s).to eql("#{protocol}://#{subdomain}.ably.io")
+          expect(subject.uri.to_s).to eql("#{protocol}://main.realtime.ably.net")
         end
       end
 
@@ -270,7 +262,7 @@ def rest?
       context 'when set without custom fallback hosts configured' do
         let(:environment) { 'foo' }
         let(:client_options) { default_options.merge(environment: environment) }
-        let(:default_fallbacks) { %w(a b c d e).map { |id| "#{environment}-#{id}-fallback.ably-realtime.com" } }
+        let(:default_fallbacks) { %w(a b c d e).map { |id| "#{environment}.#{id}.fallback.ably-realtime.com" } }
 
         it 'sets the environment attribute' do
           expect(subject.environment).to eql(environment)
@@ -298,7 +290,7 @@ def rest?
       context 'when set with fallback_hosts_use_default' do
         let(:environment) { 'foo' }
         let(:custom_fallbacks) { %w(a b c).map { |id| "#{environment}-#{id}.foo.com" } }
-        let(:default_production_fallbacks) { %w(a b c d e).map { |id| "#{id}.ably-realtime.com" } }
+        let(:default_production_fallbacks) { %w(a b c d e).map { |id| "main.#{id}.fallback.ably-realtime.com" } }
         let(:client_options) { default_options.merge(environment: environment, fallback_hosts_use_default: true) }
 
         it 'sets the environment attribute' do
diff --git a/spec/support/test_app.rb b/spec/support/test_app.rb
index 2e7fc394..e1bf93ae 100644
--- a/spec/support/test_app.rb
+++ b/spec/support/test_app.rb
@@ -57,7 +57,7 @@ def restricted_api_key
   def delete
     return unless TestApp.instance_variable_get('@singleton__instance__')
 
-    url = "#{sandbox_client.endpoint}/apps/#{app_id}"
+    url = "#{sandbox_client.uri}/apps/#{app_id}"
 
     basic_auth = Base64.urlsafe_encode64(api_key).chomp
     headers    = { "Authorization" => "Basic #{basic_auth}" }
@@ -66,11 +66,11 @@ def delete
   end
 
   def environment
-    ENV['ABLY_ENV'] || 'sandbox'
+    ENV['ABLY_ENV'] || 'nonprod:sandbox'
   end
 
   def create_test_app
-    url = "#{sandbox_client.endpoint}/apps"
+    url = "#{sandbox_client.uri}/apps"
 
     headers = {
       'Accept'       => 'application/json',
@@ -86,7 +86,7 @@ def create_test_app
   end
 
   def host
-    sandbox_client.endpoint.host
+    sandbox_client.uri.host
   end
 
   def realtime_host
@@ -94,12 +94,13 @@ def realtime_host
   end
 
   def create_test_stats(stats)
-    client = Ably::Rest::Client.new(key: api_key, environment: environment)
+    client = Ably::Rest::Client.new(key: api_key, endpoint: environment)
     response = client.post('/stats', stats)
     raise "Could not create stats fixtures.  Ably responded with status #{response.status}\n#{response.body}" unless (200..299).include?(response.status)
   end
 
   private
+
   def sandbox_client
     @sandbox_client ||= Ably::Rest::Client.new(key: 'app.key:secret', tls: true, environment: environment)
   end
diff --git a/spec/unit/models/http_paginated_result_spec.rb b/spec/unit/models/http_paginated_result_spec.rb
index 1c4ac199..cb8ef1bc 100644
--- a/spec/unit/models/http_paginated_result_spec.rb
+++ b/spec/unit/models/http_paginated_result_spec.rb
@@ -23,7 +23,7 @@
       status: status
     })
   end
-  let(:base_url) { 'http://rest.ably.io/channels/channel_name' }
+  let(:base_url) { 'http://main.realtime.ably.net/channels/channel_name' }
   let(:full_url) { "#{base_url}/whatever?param=exists" }
   let(:paginated_result_options) { Hash.new }
   let(:first_paged_request) { paginated_result_class.new(http_response, full_url, client, paginated_result_options) }
@@ -193,7 +193,7 @@
   end
 
   context 'with paged http response' do
-    let(:base_url) { 'http://rest.ably.io/channels/channel_name' }
+    let(:base_url) { 'http://main.realtime.ably.net/channels/channel_name' }
     let(:full_url) { "#{base_url}/messages" }
     let(:headers) do
       {
diff --git a/spec/unit/realtime/connection_spec.rb b/spec/unit/realtime/connection_spec.rb
index 9c227af0..08e66733 100644
--- a/spec/unit/realtime/connection_spec.rb
+++ b/spec/unit/realtime/connection_spec.rb
@@ -2,7 +2,7 @@
 require 'shared/protocol_msgbus_behaviour'
 
 describe Ably::Realtime::Connection do
-  let(:client) { instance_double('Ably::Realtime::Client', logger: double('logger').as_null_object, recover: nil, endpoint: double('endpoint', host: 'realtime.ably.io')) }
+  let(:client) { instance_double('Ably::Realtime::Client', logger: double('logger').as_null_object, recover: nil, uri: double('uri', host: 'main.realtime.ably.net')) }
 
   subject do
     Ably::Realtime::Connection.new(client, {}).tap do |connection|