add-a-store

Add a store

A service is a named interface for one job. Its port declares the operations that callers need. An adapter implements those operations for a storage provider.

Effect describes work with typed failures and required dependencies. Schema defines accepted values and their runtime checks.

A Layer builds services and supplies their construction dependencies. Alchemy declares and deploys cloud resources through Effect programs.

A capability is one named action with shared value definitions and a server-side implementation.

Read AGENTS.md first. Follow its source-first rules before changing Effect or Alchemy code. Start from packages/database and check which storage requirements it meets.

1. Name the facts and their owner

• Name the stored data, its system of record, and the writer.
• Mark copies calculated from source data. Describe how to rebuild them, how current they are, and their consistency guarantees.
• Read packages/database/src/model.ts and packages/database/src/run-log.ts.
• Reuse RunLog when its person-scoped completed-run facts and operation guarantees fit the job.
• Name genuinely different facts before adding another store. Anonymous execution starts do not fit today's RunLog schema.
• Keep observational reporting failures from changing whether unrelated capabilities run or what they return, as request capture does in packages/events.
• If completeness requires gating execution, make that availability tradeoff an explicit product decision.
• Check composition before assuming recording exists. The deployed site does not currently provide or call RunLog.
• For a repeated aggregate, compare a bounded query with a keyed read model. Do not scan all history per page request.
• Write the authoritative fact once. Independent writes to source and aggregate cannot guarantee consistency.

Read skills/rat-stack-mode/principles/name-the-system-of-record.md and skills/rat-stack-mode/principles/no-dual-writes.md.

2. Define operations for the application job

• Copy the service shape in packages/database/src/run-log.ts.
• Give the port small named operations. Keep SQL, Drizzle, and vendor resources out of its callers.
• Put schemas and expected failures beside the port, as in packages/database/src/model.ts.
• Distinguish InvalidDatabaseInput from DatabaseError. Preserve operation and source cause.
• Define retries and operation identity explicitly. RunLog.record generates a fresh UUIDv7 for each call; it is not replay-idempotent.

The existing port has no atomic multi-write operation. Do not imply that two port calls share a transaction. If a source write and cursor must commit together, design that operation before building the adapter.

3. Validate input and decode stored rows

• Decode input before issuing storage statements, as RunLog.record and RunLog.listRecent do.
• Reject invalid input with InvalidDatabaseInput before storage work starts.
• Decode unknown returned rows with PersistedRunLogRowSchema in packages/database/src/store.ts.
• Decode the domain entry too. Reject mismatched outcome and failure fields instead of silently repairing them.
• Keep adapter failures typed as DatabaseError.

Read skills/rat-stack-mode/principles/validate-before-durable-write.md.

4. Implement each vendor and bound reads

• Read packages/database/src/vendor.ts and packages/database/src/run-log-vendor.ts.
• Keep each vendor's Drizzle operations in the cartridge, a package for one job with its implementation and required infrastructure. Choose one Layer with the exhaustive DatabaseVendorResource union.
• Name each read's key, index, ordering, row budget, and pagination rule.
• ListRecentRunsInputSchema bounds results to 1–100; adapters apply the person filter and limit.
• Inspect query plans. A bounded result can still scan many rows.
• Measure before choosing new operational limits. Label unmeasured values as guesses.

Read skills/rat-stack-mode/principles/bound-every-read.md and skills/rat-stack-mode/principles/measure-real-limits.md.

5. Carry schemas, migrations, and resources together

• Follow packages/database/src/schema/d1.ts and packages/database/src/schema/postgres.ts.
• Keep each dialect's migrations under packages/database/migrations/.
• Read packages/database/src/migrations.ts for paths that work outside the package directory.
• Follow packages/database/src/d1.ts or packages/database/src/hyperdrive-postgres.ts for resource-owning Layers.
• Keep connection strings redacted. Do not expose credentials through the port or failure messages.
• Follow packages/database/src/postgres-migrations.ts for deploy-time registration.
• Review infrastructure plans under AGENTS.md's approval rules. A schema change is not permission to delete a resource.

6. Prove the behavior on every storage implementation

Use packages/database/test/run-log.test.ts and packages/database/test/local-layers.ts as the executable references.

• Run the same behavior checks against D1 with local SQLite and Hyperdrive Postgres with PGlite.
• Check outcome variants, person isolation, ordering, limits, invalid inputs, and typed storage failures.
• Check replay and interrupted execution when the new operation promises idempotency or atomicity.
• Check migration paths with packages/database/test/migration-paths.test.ts.
• Prefer generated properties and command histories for new domain behavior. Plant a violation and observe failure before trusting them.

The current tests compare both storage implementations with examples. Deployed-provider behavior and vendor switching remain unproven. Name those gaps when reporting. Add real-infrastructure proof when the runtime differs from these substitutes.

7. Compose, validate, and report

Provide the chosen Layer at the app's composition root. Expose new actions through add-a-capability. For stateful workflows, also follow add-a-lifecycle-machine. Run pnpm turbo run check test build and fix failures without weakening the fence. The fence is the compiler checks, lint rules, and hooks that reject prohibited code and shortcuts.

Report:

• The port, operations, system of record, and derived copies.
• Vendor choice, schema changes, migrations, and resource-plan actions.
• Read bounds, query-plan evidence, and measured limits or explicit guesses.
• Validation, backend test results, replay proof, and atomicity gaps.
• Composition wiring and what remains unproven on deployed infrastructure.