Postgres WASM by Snaplet and Supabase

Summary

Supabase and Snaplet open-sourced postgres-wasm, a PostgreSQL server that runs inside a browser and supports browser persistence, pg_dump restoration, and logical replication with a remote database. Rather than compiling PostgreSQL directly to WebAssembly, the project packages a stripped-down Linux image with PostgreSQL in a Buildroot-based virtual machine, then runs it through v86 in the browser. PostgreSQL 14 startup failures were resolved by disabling v86 JIT compilation, while image optimization used a compressed 9P filesystem, asynchronous HTTPS loading, and page_poison=on to produce an initial state of about 12MB. Websocket proxying provides outbound connectivity and a forked proxy with nginx tunnels incoming connections to PostgreSQL. The project remains experimental because the download is currently about 30MB, but the post identifies offline data, testing, development environments, snapshots, and support as potential uses.

Takeaways

1. 1

   PostgreSQL 14 failed during initialization with segmentation faults until v86 JIT compilation was disabled; switching PostgreSQL from POSIX to System V memory management also resolved the issue with the current v86 release.

2. 2

   The optimized compressed initial state is about 12MB and includes a running network state, PostgreSQL 14.4, and psql; caching that state makes subsequent refreshes feel almost instant.

3. 3

   Websocket proxying supports outbound traffic and database imports, while the forked proxy maps incoming connections to browser-hosted PostgreSQL instances for tools such as PgAdmin4.