Deploy a feature flag service on Val.town powered by nano-supabase with persistent storage.

• Full PostgreSQL database running in WebAssembly
• Supabase-compatible query API
• Per-environment overrides and app scoping
• Percentage-based rollouts with deterministic hashing
• Persistent storage via PGlite's dumpDataDir/loadDataDir (data survives cold starts)
• CORS enabled for browser access

1. Go to val.town and create a new val
2. Copy the contents of all .ts files (index.ts, persistence.ts, schema.ts) into the editor
3. Important: Set the val type to HTTP using the dropdown near the val name
4. Your API is instantly live at https://YOUR_USERNAME-YOUR_VAL_NAME.web.val.run

npm install -g @valtown/vt

vt login

cd examples/valtown
vt create my-flags . --no-editor-files --upload-if-exists --public

# Set the val type to HTTP on the web page
vt browse

./test.sh https://YOUR_USERNAME-YOUR_VAL_NAME.web.val.run

Or test manually:

# Create a flag with 50% rollout
curl -X POST https://YOUR_URL/flags \
  -H "Content-Type: application/json" \
  -d '{"name": "dark-mode", "enabled": true, "rollout_percentage": 50}'

# Add a production override (disabled)
curl -X POST https://YOUR_URL/flags/dark-mode/environments \
  -H "Content-Type: application/json" \
  -d '{"environment": "production", "enabled": false}'

# Scope to a specific app
curl -X POST https://YOUR_URL/flags/dark-mode/apps \
  -H "Content-Type: application/json" \
  -d '{"app_name": "web-app"}'

# Evaluate: is this flag active for web-app in staging?
curl "https://YOUR_URL/flags/dark-mode/evaluate?app=web-app&environment=staging&identifier=user-123"

# Toggle a flag
curl -X POST https://YOUR_URL/flags/dark-mode/toggle

When evaluating a flag (GET /flags/:name/evaluate?app=x&environment=y):

1. If the flag doesn't exist -> active: false (flag_not_found)
2. If the flag has app scopes and the requested app isn't listed -> active: false (app_not_scoped)
3. If an environment override exists, its enabled value takes precedence over the global flag enabled
4. If resolved enabled is false -> active: false (disabled)
5. If rollout_percentage < 100, a deterministic hash of the identifier param decides inclusion. Without an identifier, it uses random selection -> active: false (rollout_excluded)
6. Otherwise -> active: true

The database is persisted using PGlite's built-in dumpDataDir/loadDataDir. On each write operation, the entire database is serialized as a gzipped tarball and stored in Val.town's blob storage. On cold start, the snapshot is loaded back, restoring all tables, indexes, and data atomically.

The blob key is nano-supabase-flags-db.

• index.ts - HTTP handler with all feature flag endpoints
• persistence.ts - Database initialization and snapshot persistence
• schema.ts - Table definitions (feature_flags, flag_environments, flag_apps)

"Not found" response: The val type isn't set to HTTP. Go to the val's page and change the type dropdown to "HTTP".

"Invalid version provided" error: Try deleting the val and creating a new one with a different name, or clear Val.town's module cache by changing the import URL (add ?v=2).

Import errors: Make sure you're using the exact versions specified in the import statements.