HydraCache 0.35.0

HydraCache 0.35.0

0.35.0 is a database production-readiness release. It focuses on making the
existing database result-cache layer safer to adopt in real Rust services
through transaction-safe invalidation guidance, key/tag checklists, adapter
parity coverage, database-focused observability, and release-gate clarity.

Highlights

• Database production-readiness guide for explicit, local-first query-result
  caching.
• Transaction-safe invalidation examples that invalidate only after successful
  commits.
• Cache key and tag safety checklist for tenant, authorization, filter,
  pagination, sorting, locale, region, feature flag, and time-window dimensions.
• Adapter error-context hardening for SQLx, Diesel, SeaORM, and repository
  loaders where it can be done without making adapters own query execution.
• SQLx reference scenarios for exactly-one, optional, collection, repository,
  transaction-owned, negative-cache, and Postgres smoke-test flows.
• Diesel and SeaORM parity coverage for common result shapes and failure
  behavior.
• Database-cache observability guidance that maps core counters to loader
  avoidance, single-flight activity, invalidation, stale fallback, and load
  failures.
• Sandbox production-readiness demo path for miss, hit, update, rollback,
  invalidation, reload, and diagnostics flows.

Changes

• Added docs/DB_PRODUCTION_READINESS.md as the central production checklist
  for database result caching.
• Linked the database readiness guide from the README and policy guide.
• Tracked the 0.35.0 implementation plan under
  docs/plans/V0_35_DATABASE_PRODUCTION_READINESS_PLAN.md.
• Added policy-guide coverage for tenant, permission, escaped filter,
  pagination, sorting, collection-tag, and unsafe-key documentation scenarios.
• Added transaction-safe invalidation tests for failed writes, rollback,
  committed update, committed insert, committed delete, and repeated
  invalidation.
• Added DbOperationContext, DbAdapterKind, and DbResultShape so
  database-cache errors include adapter, operation, namespace, key, and result
  shape context.
• Labeled SQLx, Diesel, and SeaORM helper errors with adapter-specific result
  shapes while keeping the database libraries responsible for typed database
  errors.
• Expanded DbCacheError::MissingKey with adapter, namespace, and result-shape
  fields. This is a pre-1.0 diagnostic API adjustment; callers matching the
  variant should use .. for forward-compatible pattern matches.
• Strengthened SQLx SQLite reference coverage for transaction commit/rollback
  invalidation timing and SQLx loader-failure retry/context behavior.
• Added Diesel and SeaORM transaction timing parity tests for rollback,
  commit-then-invalidate, and cached-value reload behavior.
• Added DB-cache observability contract guidance and database-neutral
  diagnostics tests for hit/miss/load counters, single-flight joins,
  invalidation counts, stale load discard, and stale fallback after loader
  failure.

Verification

This release should pass:

• cargo fmt --all -- --check
• cargo check --workspace --all-targets --locked
• cargo test --workspace --all-targets --locked
• cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
• cargo test --doc --workspace --locked
• RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps --locked
• .\scripts\verify-release-readiness.ps1 -Version 0.35.0 -RunGate
• cargo test -p hydracache-db --locked
• cargo test -p hydracache-sqlx --locked
• cargo test -p hydracache-diesel --locked
• cargo test -p hydracache-seaorm --locked
• cargo test --doc -p hydracache-db --locked
• cargo test --doc -p hydracache-sqlx --locked
• cargo test --doc -p hydracache-diesel --locked
• cargo test --doc -p hydracache-seaorm --locked
• cargo package -p hydracache-db --allow-dirty
• cargo package -p hydracache-sqlx --allow-dirty
• cargo package -p hydracache-diesel --allow-dirty
• cargo package -p hydracache-seaorm --allow-dirty

Optional real Postgres coverage should pass or skip gracefully when Docker is
not available:

• cargo test -p hydracache-sqlx --test postgres_testcontainers --locked -- --nocapture