ADR 0018: explicit Cloud SQL tiers select their compatible edition¶
Status: accepted, 2026-10-18.
Context¶
The reference run encountered Enterprise Plus capacity failures in several zones. Google currently supports MySQL 8.4 on Enterprise as well as Enterprise Plus. The provider previously forced Plus for 8.4, rejecting dedicated custom tiers. Changing the engine version would break the selected Magento recipe.
Decision¶
Keep the existing MySQL 8.4 default: Enterprise Plus with
db-perf-optimized-N-2. An explicit target.gcp.cloudSqlTier dedicated-core
db-custom-<cpus>-<memoryMB> selects Enterprise. Validate the documented CPU,
memory and alignment limits before planning. Other new machine families remain
outside this change. MySQL 8.0 behavior is preserved.
The regional admission check still reads Google's tier catalog and fails on read errors. Custom combinations are not enumerated there; a valid custom shape needs a matching regional dedicated-core series entry. Exact predefined tiers keep their existing regional checks. Neither check guarantees allocation capacity.
No YAML field, manifest, provider RPC or alternate state store is added.
Consequences¶
Unchanged configuration keeps the same edition and tier. A deliberate custom tier change on an existing Plus instance can request an edition downgrade and cause downtime. Preview that change and test it outside production first. Edition and tier remain visible to Pulumi; neither is ignored. Creation-only zone handling from ADR 0017 remains unchanged.
Tests cover real resource inputs, default preservation, custom limits and regional catalog handling. Acceptance with published provider 0660426 allocated MySQL 8.4 Enterprise with the explicit dedicated tier successfully. Application acceptance and migration of an existing Plus instance remain separate checks. A stockout is handled through the existing diagnostic and retained state, without automatic retries.