docs adr 005 modular monolith and postgresql

ADR-005: One Go monolith and one PostgreSQL/PostGIS database

Status: Adopted for planning. Date: 2026-09-28. Scope: planned platform; implementation evidence required by roadmap gates.

Context

A small team needs clear ownership and dependable jobs without multiple operational systems.

Decision

Go net/http/chi/pgx/sqlc/slog; API/worker/migrator from one codebase/release. PostgreSQL/PostGIS is authoritative. Explicit module ports/SQL ownership; queue rows inserted with business facts and claimed with leases/fencing. No external broker/cache initially.

Alternatives

Microservices; managed proprietary backend; Redis/broker queues; generic ORM.

Consequences

Simple deploy and transactions, but one DB/VPS creates a failure domain. Dedicated database/replicas later require measured justification. Queue correctness still requires idempotent effects and real concurrency tests.

Validation and follow-up

Use the owning tasks in ROADMAP, specifications in docs index and decision log. Record tested policy/tool versions before marking a release gate complete.