0016-fate-pure-transport-effect-services-domain.md

id	14
title	fate is pure transport; Effect services stay the domain
status	accepted
date	2026-05-23
tags	fate effect architecture sources

0016 — fate is pure transport; Effect services stay the domain

Context

fate ships an opinionated Drizzle source adapter (createDrizzleSourceAdapter) that queries the database directly and resolves views from rows. phoenix already has its whole domain in Effect Context.Services over Drizzle — keyset pagination, validation, the vote/karma engine, authorization. Using fate's adapter would bypass that and re-home domain logic into view fields.

Decision

fate never touches the database. Every read and write goes through an Effect service method:

• We hand-build a SourceResolver whose byId/byIds/connection executors delegate to service methods. Each SourceDefinition is a plain object literal and the registry is a Map keyed by it — fate's createSourceDefinition/getDataViewSourceConfig/createSourceRegistry helpers are internal and unexported in 1.0.3, and createDrizzleSourceAdapter (the only public source builder) is never used.
• Resolvers and source executors are Effect generators wrapped by a bridge helper family — fateQuery / fateList / fateMutation / fateSource — that runs them through the per-request runtime and maps failures to wire errors. No runtime.runPromise* outside the bridge.
• Every type reachable as a relation implements byIds (a WHERE id IN (...) over the read path) to avoid N+1.

Consequences

• Easier: domain logic stays in one place; services are untouched; tracing and error mapping are consistent with the rest of the backend.
• Harder: more wiring than the adapter; services gain getXsByIds methods where missing.
• Banned: the fate Drizzle adapter, database access inside views, and raw runtime calls in feature/resolver code.
• See fate-effect-sources.md and fate-effect-server.md (bridge doc retired, ADR 0042).