API Platform 4.3 — Performance

Use when

• The API is slower than expected, especially on list endpoints.
• A max_joins: 30 exception fires because the entity has many relations.
• Memory blows up on large collections.
• p99 latency is above ~50 ms for simple routes.
• Cache invalidation cannot keep up with writes.

Default workflow

1. Detect the force_eager: true trap. Switch to false and replace with targeted join fetches in repositories.
2. Profile with the Symfony profiler in dev — look for N+1 patterns.
3. For list views: project a DTO via DQL NEW App\Dto\PostListItem(...) instead of hydrating the full entity.
4. Enable APCu for resource metadata cache in prod.
5. Adopt FrankenPHP worker mode for high-traffic APIs (stateful kernel between requests).
6. Add HTTP cache headers per operation and cacheTags for invalidation.

Guardrails

• force_eager: true is the 4.x default but rarely what you want for an entity with many relations. Set it to false and use targeted addSelect() join fetches per query.
• #[ApiProperty(fetchEager: true)] for specific fields only — never blanket eager loading.
• Never iterate without clear() on million-row collections — memory will explode.
• HTTP cache + write paths must agree on invalidation — purge cacheTags on every write.
• FrankenPHP worker mode requires worker-safe code (no static state leaks).

Progressive disclosure

• SKILL.md covers posture and rules.
• reference.md carries the full patterns: fetch modes, eager loading trap, join fetch recipe, DTO projection, batch iteration, HINT_READ_ONLY, APCu metadata cache, FrankenPHP worker, HTTP cache headers, cache tags + Varnish PURGE, dynamic Last-Modified listener.

Output contract

• eager_loading.force_eager: false confirmed (or documented exception).
• Repository methods using targeted addSelect() for list endpoints.
• DTO projections via DQL NEW for large lists.
• APCu metadata cache configured in prod.
• HTTP cache configured per operation (where applicable).
• cacheTags purged on writes.
• p99 latency measured before/after.

References

• reference.md