1---
2title: "Post-mortem: A Backward Incompatible Database Migration"
3description: Val runs failed due to a database migration that was not backward compatible
4pubDate: 2025-04-02T00:00:00.000Z
5author: Sophie Houser
6---
7
8Today at 10:11am we experienced a 12-minute outage, which caused HTTP vals to return 503 errors and other types of vals to fail. In the end, the root cause was a deployment timing issue where database migrations were deployed successfully, but our application code deployment hung for several minutes. The new database migrations were incompatible with the old application code and crashed the process.
9
10We aim to make all database migrations maintain backward compatibility, but in this case, we only discovered through the delayed deployment feedback that the new migrations were not compatible with previous versions.
11
12## Timeline
27## Next Steps
28
29Reliability is important to us and we’ve taken steps to make sure this doesn’t happen again. We’ve added a test to ensure database migrations are backward compatible, which we’ll run before we deploy any new code that includes database migrations.
9- The **client-side entrypoint** is `/frontend/index.html`, which in turn imports `/frontend/index.tsx`, which in turn imports the React app from `/frontend/components/App.tsx`.
10
11[React Hono Example](https://www.val.town/x/stevekrouse/reactHonoExample) is a fuller featured example project, with a SQLite database table, queries, client-side CSS and a favicon, and some shared code that runs on both client and server.
1import { generateCode } from "./backend/generate-code";
2import { createTables } from "./database/migrations";
3import { createProject, getCode, getNextVersionNumber, insertVersion } from "./database/queries";
4
5async function servePublicFile(path: string): Promise<Response> {
9- The **client-side entrypoint** is `/frontend/index.html`, which in turn imports `/frontend/index.tsx`, which in turn imports the React app from `/frontend/components/App.tsx`.
10
11[React Hono Example](https://www.val.town/x/stevekrouse/reactHonoExample) is a fuller featured example project, with a SQLite database table, queries, client-side CSS and a favicon, and some shared code that runs on both client and server.
9- The **client-side entrypoint** is `/frontend/index.html`, which in turn imports `/frontend/index.tsx`, which in turn imports the React app from `/frontend/components/App.tsx`.
10
11[React Hono Example](https://www.val.town/x/stevekrouse/reactHonoExample) is a fuller featured example project, with a SQLite database table, queries, client-side CSS and a favicon, and some shared code that runs on both client and server.
46 "slug": "codegen",
47 "link": "/blog/codegen",
48 "description": "Like Claude Artifacts, but with a backend and database",
49 "pubDate": "Thu, 22 Aug 2024 00:00:00 GMT",
50 "author": "JP Posma",
1---
2title: "Post-mortem: A Backward Incompatible Database Migration"
3description: Val runs failed due to a database migration that was not backward compatible
4pubDate: 2025-04-02T00:00:00.000Z
5author: Sophie Houser
6---
7
8Today at 10:11am we experienced a 12-minute outage, which caused HTTP vals to return 503 errors and other types of vals to fail. In the end, the root cause was a deployment timing issue where database migrations were deployed successfully, but our application code deployment hung for several minutes. The new database migrations were incompatible with the old application code and crashed the process.
9
10We aim to make all database migrations maintain backward compatibility, but in this case, we only discovered through the delayed deployment feedback that the new migrations were not compatible with previous versions.
11
12## Timeline
27## Next Steps
28
29Reliability is important to us and we’ve taken steps to make sure this doesn’t happen again. We’ve added a test to ensure database migrations are backward compatible, which we’ll run before we deploy any new code that includes database migrations.
34 todayHits = hits.todayHits;
35 } catch (e) {
36 console.log("Caught database error: ", e);
37 }
38 if (url.pathname === "/") {
1import { generateCode } from "./backend/generate-code";
2import { createTables } from "./database/migrations";
3import { createProject, getCode, getNextVersionNumber, insertVersion } from "./database/queries";
4
5async function servePublicFile(path: string): Promise<Response> {
9- The **client-side entrypoint** is `/frontend/index.html`, which in turn imports `/frontend/index.tsx`, which in turn imports the React app from `/frontend/App.tsx`.
10
11[React Hono Example](https://www.val.town/x/stevekrouse/reactHonoExample) is a fuller featured example project, with a SQLite database table, queries, client-side CSS and a favicon, and some shared code that runs on both client and server.