diff --git a/webapp/.gitignore b/webapp/.gitignore
index 7507a42..3b34769 100644
--- a/webapp/.gitignore
+++ b/webapp/.gitignore
@@ -31,3 +31,6 @@ npm-debug.log*
 # typescript
 *.tsbuildinfo
 next-env.d.ts
+
+# Lyra
+store.json
diff --git a/webapp/src/Cache.ts b/webapp/src/Cache.ts
deleted file mode 100644
index 9c915ee..0000000
--- a/webapp/src/Cache.ts
+++ /dev/null
@@ -1,45 +0,0 @@
-/* global globalThis */
-
-import { LanguageNotSupported } from '@/errors';
-import { LyraProjectConfig } from '@/utils/lyraConfig';
-import { ProjectStore } from '@/store/ProjectStore';
-import { RepoGit } from '@/RepoGit';
-import { ServerConfig } from '@/utils/serverConfig';
-import { Store } from '@/store/Store';
-import YamlTranslationAdapter from '@/utils/adapters/YamlTranslationAdapter';
-import MessageAdapterFactory from './utils/adapters/MessageAdapterFactory';
-
-export class Cache {
-  public static async getLanguage(projectName: string, lang: string) {
-    const serverProjectConfig =
-      await ServerConfig.getProjectConfig(projectName);
-    const repoGit = await RepoGit.getRepoGit(serverProjectConfig);
-    const lyraConfig = await repoGit.getLyraConfig();
-    const lyraProjectConfig = lyraConfig.getProjectConfigByPath(
-      serverProjectConfig.projectPath,
-    );
-    if (!lyraProjectConfig.isLanguageSupported(lang)) {
-      throw new LanguageNotSupported(lang, projectName);
-    }
-    const store = await Cache.getProjectStore(lyraProjectConfig);
-    return store.getTranslations(lang);
-  }
-
-  public static async getProjectStore(
-    lyraProjectConfig: LyraProjectConfig,
-  ): Promise<ProjectStore> {
-    if (!globalThis.store) {
-      globalThis.store = new Store();
-    }
-
-    if (!globalThis.store.hasProjectStore(lyraProjectConfig.absPath)) {
-      const projectStore = new ProjectStore(
-        MessageAdapterFactory.createAdapter(lyraProjectConfig),
-        new YamlTranslationAdapter(lyraProjectConfig.absTranslationsPath),
-      );
-      globalThis.store.addProjectStore(lyraProjectConfig.absPath, projectStore);
-    }
-
-    return globalThis.store.getProjectStore(lyraProjectConfig.absPath);
-  }
-}
diff --git a/webapp/src/RepoGit.ts b/webapp/src/RepoGit.ts
index 2231f60..ffd04b1 100644
--- a/webapp/src/RepoGit.ts
+++ b/webapp/src/RepoGit.ts
@@ -4,7 +4,6 @@ import { Octokit } from '@octokit/rest';
 import path from 'path';
 import { stringify } from 'yaml';
 
-import { Cache } from '@/Cache';
 import { IGit } from '@/utils/git/IGit';
 import { LyraConfig } from '@/utils/lyraConfig';
 import packageJson from '../package.json';
@@ -15,6 +14,7 @@ import { debug, info, warn } from '@/utils/log';
 import { WriteLanguageFileError, WriteLanguageFileErrors } from '@/errors';
 import { type TranslationMap } from '@/utils/adapters';
 import { getTranslationsBySourceFile } from '@/utils/translationObjectUtil';
+import { Store } from '@/store/Store';
 
 export class RepoGit {
   private static repositories: {
@@ -83,7 +83,7 @@ export class RepoGit {
   public async saveLanguageFiles(projectPath: string): Promise<string[]> {
     const lyraConfig = await this.getLyraConfig();
     const projectConfig = lyraConfig.getProjectConfigByPath(projectPath);
-    const projectStore = await Cache.getProjectStore(projectConfig);
+    const projectStore = await Store.getProjectStore(projectConfig);
     const languages = await projectStore.getLanguageData();
 
     return await this.writeLangFiles(
diff --git a/webapp/src/actions/updateTranslation.ts b/webapp/src/actions/updateTranslation.ts
index 58b1bdf..879ab5d 100644
--- a/webapp/src/actions/updateTranslation.ts
+++ b/webapp/src/actions/updateTranslation.ts
@@ -1,7 +1,7 @@
 'use server';
 
-import { Cache } from '@/Cache';
 import { RepoGit } from '@/RepoGit';
+import { Store } from '@/store/Store';
 import { ServerConfig } from '@/utils/serverConfig';
 import { MessageNotFound } from '@/errors';
 
@@ -78,7 +78,7 @@ export default async function updateTranslation(
     };
   }
 
-  const projectStore = await Cache.getProjectStore(projectConfig);
+  const projectStore = await Store.getProjectStore(projectConfig);
 
   const messages = await projectStore.getMessages();
   const messageIds = messages.map((message) => message.id);
@@ -90,6 +90,7 @@ export default async function updateTranslation(
 
   try {
     await projectStore.updateTranslation(languageName, messageId, translation);
+    await Store.persistToDisk();
   } catch (e) {
     return {
       errorMessage: 'Failed to update translation',
diff --git a/webapp/src/dataAccess.ts b/webapp/src/dataAccess.ts
index 8858f71..0518e01 100644
--- a/webapp/src/dataAccess.ts
+++ b/webapp/src/dataAccess.ts
@@ -1,7 +1,8 @@
-import { Cache } from '@/Cache';
 import { RepoGit } from '@/RepoGit';
 import { ServerConfig, ServerProjectConfig } from '@/utils/serverConfig';
 import { getTranslationsIdText } from './utils/translationObjectUtil';
+import { LanguageNotSupported } from './errors';
+import { Store } from '@/store/Store';
 
 export async function accessProjects() {
   const serverConfig = await ServerConfig.read();
@@ -41,12 +42,16 @@ export async function accessLanguage(
   await repoGit.checkoutBaseAndPull();
   const lyraConfig = await repoGit.getLyraConfig();
   const projectConfig = lyraConfig.getProjectConfigByPath(project.projectPath);
-  const projectStore = await Cache.getProjectStore(projectConfig);
+  const projectStore = await Store.getProjectStore(projectConfig);
   const messages = await projectStore.getMessages();
-  const translationsWithFilePath = await Cache.getLanguage(
-    projectName,
-    languageName,
-  );
+
+  if (!projectConfig.isLanguageSupported(languageName)) {
+    throw new LanguageNotSupported(languageName, projectName);
+  }
+
+  const translationsWithFilePath =
+    await projectStore.getTranslations(languageName);
+
   const translations = getTranslationsIdText(translationsWithFilePath);
 
   return {
@@ -61,7 +66,7 @@ async function readProject(project: ServerProjectConfig) {
   await repoGit.checkoutBaseAndPull();
   const lyraConfig = await repoGit.getLyraConfig();
   const projectConfig = lyraConfig.getProjectConfigByPath(project.projectPath);
-  const store = await Cache.getProjectStore(projectConfig);
+  const store = await Store.getProjectStore(projectConfig);
   const messages = await store.getMessages();
   const languagesWithTranslations = projectConfig.languages.map(
     async (lang) => {
diff --git a/webapp/src/errors.ts b/webapp/src/errors.ts
index 0f5fead..b775022 100644
--- a/webapp/src/errors.ts
+++ b/webapp/src/errors.ts
@@ -1,9 +1,3 @@
-export class LanguageNotFound extends Error {
-  constructor(lang: string) {
-    super(`Language ${lang} not found`);
-  }
-}
-
 export class LanguageNotSupported extends Error {
   constructor(lang: string, projectName: string) {
     super(`Language ${lang} is not supported in project ${projectName}`);
diff --git a/webapp/src/store/ProjectStore.spec.ts b/webapp/src/store/ProjectStore.spec.ts
index 06cbcb0..b323d3d 100644
--- a/webapp/src/store/ProjectStore.spec.ts
+++ b/webapp/src/store/ProjectStore.spec.ts
@@ -1,7 +1,6 @@
 import { describe, expect, it, jest } from '@jest/globals';
 
 import { ProjectStore } from './ProjectStore';
-import { LanguageNotFound } from '@/errors';
 import { IMessageAdapter } from '@/utils/adapters';
 
 function mockMsgAdapter(): jest.Mocked<IMessageAdapter> {
@@ -58,7 +57,7 @@ describe('ProjectStore', () => {
     });
   });
 
-  it('throws exception for missing language', async () => {
+  it('returns empty object for missing language', async () => {
     expect.assertions(1);
     const msgAdapter = mockMsgAdapter();
     msgAdapter.getMessages.mockResolvedValue([]);
@@ -66,8 +65,8 @@ describe('ProjectStore', () => {
       getTranslations: async () => ({}),
     });
 
-    const actual = projectStore.getTranslations('fi');
-    await expect(actual).rejects.toThrowError(LanguageNotFound);
+    const actual = await projectStore.getTranslations('fi');
+    expect(actual).toEqual({});
   });
 
   it('returns updated translations', async () => {
@@ -141,29 +140,6 @@ describe('ProjectStore', () => {
     });
   });
 
-  it('throws exception for missing language', async () => {
-    expect.assertions(1);
-    const msgAdapter = mockMsgAdapter();
-    msgAdapter.getMessages.mockResolvedValue([
-      {
-        defaultMessage: '',
-        id: 'greeting.headline',
-        params: [],
-      },
-    ]);
-    const projectStore = new ProjectStore(msgAdapter, {
-      getTranslations: async () => ({}),
-    });
-
-    const actual = projectStore.updateTranslation(
-      'de',
-      'greeting.headline',
-      'Hallo!',
-    );
-
-    await expect(actual).rejects.toThrowError(LanguageNotFound);
-  });
-
   it('gives full access to all languages', async () => {
     const msgAdapter = mockMsgAdapter();
     msgAdapter.getMessages.mockResolvedValue([
diff --git a/webapp/src/store/ProjectStore.ts b/webapp/src/store/ProjectStore.ts
index 3fcae17..a7477b6 100644
--- a/webapp/src/store/ProjectStore.ts
+++ b/webapp/src/store/ProjectStore.ts
@@ -5,7 +5,6 @@ import {
   MessageMap,
   TranslationMap,
 } from '@/utils/adapters';
-import { LanguageNotFound } from '@/errors';
 import { StoreData } from './types';
 import mergeStoreData from './mergeStoreData';
 
@@ -17,8 +16,9 @@ export class ProjectStore {
   constructor(
     messageAdapter: IMessageAdapter,
     translationAdapter: ITranslationAdapter,
+    initialState?: StoreData,
   ) {
-    this.data = {
+    this.data = initialState || {
       languages: {},
       messages: [],
     };
@@ -42,12 +42,9 @@ export class ProjectStore {
     await this.refresh();
 
     const language = this.data.languages[lang];
-    if (!language) {
-      throw new LanguageNotFound(lang);
-    }
 
     const output: MessageMap = {};
-    Object.entries(language).forEach(([key, messageTranslation]) => {
+    Object.entries(language ?? {}).forEach(([key, messageTranslation]) => {
       output[key] = { ...messageTranslation };
     });
 
@@ -59,11 +56,15 @@ export class ProjectStore {
     return this.data.messages;
   }
 
+  toJSON(): StoreData {
+    return this.data;
+  }
+
   async updateTranslation(lang: string, id: string, text: string) {
     await this.refresh();
 
     if (!this.data.languages[lang]) {
-      throw new LanguageNotFound(lang);
+      this.data.languages[lang] = {};
     }
 
     if (!this.data.languages[lang][id]) {
diff --git a/webapp/src/store/Store.ts b/webapp/src/store/Store.ts
index 826ccc8..08bac24 100644
--- a/webapp/src/store/Store.ts
+++ b/webapp/src/store/Store.ts
@@ -1,7 +1,84 @@
+import fs from 'fs/promises';
+
 import { ProjectStore } from '@/store/ProjectStore';
+import MessageAdapterFactory from '@/utils/adapters/MessageAdapterFactory';
+import YamlTranslationAdapter from '@/utils/adapters/YamlTranslationAdapter';
+import { LyraProjectConfig } from '@/utils/lyraConfig';
+import { StoreData } from './types';
+
+const FILE_PATH = './store.json';
 
 export class Store {
   private data = new Map<string, ProjectStore>();
+  private initialState: Record<string, StoreData | undefined> = {};
+  private writes: Promise<void> = Promise.resolve();
+
+  public static async getProjectStore(
+    lyraProjectConfig: LyraProjectConfig,
+  ): Promise<ProjectStore> {
+    /**
+     * As this function is not async,
+     * no concurrent task executes between checking and updating globalThis.
+     */
+    function initialize(): Promise<Store> {
+      if (!globalThis.store) {
+        const newStore = new Store();
+        globalThis.store = newStore
+          .loadFromDisk()
+          // TODO: this catch will never happened, since loadFromDisk catch all
+          .catch((reason) => {
+            // Forget the promise, so that the next call will retry.
+            globalThis.store = null;
+            throw reason;
+          })
+          .then(() => newStore);
+      }
+      return globalThis.store;
+    }
+
+    const store = await initialize();
+
+    if (!store.hasProjectStore(lyraProjectConfig.absPath)) {
+      const initialProjectState = store.initialState[lyraProjectConfig.absPath];
+
+      const projectStore = new ProjectStore(
+        MessageAdapterFactory.createAdapter(lyraProjectConfig),
+        new YamlTranslationAdapter(lyraProjectConfig.absTranslationsPath),
+        initialProjectState,
+      );
+      store.addProjectStore(lyraProjectConfig.absPath, projectStore);
+    }
+
+    return store.getProjectStore(lyraProjectConfig.absPath);
+  }
+
+  public static async persistToDisk(): Promise<void> {
+    const store = await globalThis.store;
+    if (!store) {
+      return;
+    }
+
+    // Retain initial data if we have not opened a ProjectStore
+    const payload = {};
+    Object.assign(payload, store.initialState, store.toJSON());
+
+    const json = JSON.stringify(payload);
+
+    // Enqueue the new write, as concurrent writeFile is unsafe.
+    store.writes = store.writes.finally(() => fs.writeFile(FILE_PATH, json));
+
+    // Await the end of the queue, which is our write, to resolve.
+    await store.writes;
+  }
+
+  public toJSON(): Record<string, unknown> {
+    const data: Record<string, StoreData> = {};
+    this.data.forEach((value, key) => {
+      data[key] = value.toJSON();
+    });
+
+    return data;
+  }
 
   public addProjectStore(projectPath: string, projectStore: ProjectStore) {
     this.data.set(projectPath, projectStore);
@@ -18,4 +95,13 @@ export class Store {
     }
     return projectStore;
   }
+
+  public async loadFromDisk(): Promise<void> {
+    try {
+      const json = await fs.readFile(FILE_PATH);
+      this.initialState = JSON.parse(json.toString());
+    } catch (err) {
+      // Do nothing. It's fine to start from scratch sometimes.
+    }
+  }
 }
diff --git a/webapp/src/store/mergeStoreData.spec.ts b/webapp/src/store/mergeStoreData.spec.ts
index fb52028..5f308b7 100644
--- a/webapp/src/store/mergeStoreData.spec.ts
+++ b/webapp/src/store/mergeStoreData.spec.ts
@@ -125,6 +125,30 @@ describe('mergeStoreData()', () => {
     const result = mergeStoreData(inMemory, fromRepo);
     expect(result).toEqual(fromRepo);
   });
+
+  it('should not return undefined if both memory and repo are falsy (undefined)', () => {
+    const inMemory: StoreData = {
+      languages: {
+        sv: {},
+      },
+      messages: [],
+    };
+
+    const fromRepo: StoreData = {
+      languages: {
+        sv: {},
+      },
+      messages: [mockMessage('any.message.id', 'Default message')],
+    };
+
+    const result = mergeStoreData(inMemory, fromRepo);
+    expect(result).toStrictEqual({
+      languages: {
+        sv: {},
+      },
+      messages: [mockMessage('any.message.id', 'Default message')],
+    });
+  });
 });
 
 const mockTranslation = (
diff --git a/webapp/src/store/mergeStoreData.ts b/webapp/src/store/mergeStoreData.ts
index ff70467..efd23c8 100644
--- a/webapp/src/store/mergeStoreData.ts
+++ b/webapp/src/store/mergeStoreData.ts
@@ -1,4 +1,5 @@
 import { StoreData } from './types';
+import { MessageTranslation } from '@/utils/adapters';
 
 export default function mergeStoreData(
   inMemory: StoreData,
@@ -26,9 +27,13 @@ export default function mergeStoreData(
         output.languages[lang] = {};
       }
 
-      output.languages[lang][message.id] =
+      const messageTranslation: MessageTranslation =
         inMemory.languages[lang]?.[message.id] ||
         fromRepo.languages[lang]?.[message.id];
+
+      if (messageTranslation) {
+        output.languages[lang][message.id] = messageTranslation;
+      }
     });
   });
 
diff --git a/webapp/src/types.ts b/webapp/src/types.ts
index a05f444..ac8df7a 100644
--- a/webapp/src/types.ts
+++ b/webapp/src/types.ts
@@ -3,6 +3,12 @@ import { Store } from '@/store/Store';
 export type LanguageMap = Map<string, Record<string, string>>;
 
 declare global {
+  /**
+   * Either we promised to complete initialization,
+   * or we are ready to initialize.
+   *
+   * Every concurrent task can await the same initialization.
+   */
   // eslint-disable-next-line
-  var store: Store;
+  var store: Promise<Store> | null;
 }