Behind the Scenes: Running SQLite inside Wasm in the Browser

SQLancer executes user database exercises client-side. Let's see how compile targets and WebAssembly allow SQLite sandboxing inside the web browser.

1. Why SQLite-Wasm?

Setting up database servers for millions of users is expensive and requires complex backend security isolation. By compiling the C codebase of SQLite into WebAssembly (Wasm), we run a complete, secure database engine directly inside the browser's JavaScript runtime.

// Simulated SQLite WASM execution call
const db = new SQL.Database();
const res = db.exec("SELECT * FROM sandbox_table;");
console.log(res);

2. Storage Persistence

Wasm SQLite runs completely in-memory by default. To preserve exercises across page reloads, we leverage the browser's IndexedDB API or Origin Private File System (OPFS) to persist data blocks safely.