Performance and observability improvements

[vladiant]

Version: 1.1.0 → 1.2.0 (MINOR)

Summary

This MR addresses three performance bottlenecks and one observability gap: uncached metadata fetches, unbounded in-memory result loading, a scalar-only C++ resize path with Python list copy overhead, and a health endpoint that hardcoded its version and performed no dependency checks.

Changes

In-memory metadata cache

• Added CachedImageRepository decorator (infrastructure layer) wrapping PostgresImageRepository with a thread-safe, TTL-based in-memory cache for get_by_id lookups.
• Cache is invalidated on save and delete to maintain consistency; list_images, count, and get_expired pass through uncached.
• Configurable via IMG_CACHE_TTL_SECONDS (default 60) and IMG_CACHE_MAX_SIZE (default 1024).

Server-side cursors for list queries

• list_images() and get_expired() switched from session.execute() + .scalars().all() to session.stream_scalars() with async iteration, using PostgreSQL server-side cursors to avoid loading entire result sets into memory.

C++ SIMD optimization and zero-copy I/O

• bilinear_resize now uses SSE2 intrinsics on x86-64 to interpolate all channels per pixel in parallel (__m128 float ops), with a scalar fallback for other architectures.
• Input/output changed from std::vector<uint8_t> (copied element-by-element from/to Python lists) to py::array_t<uint8_t> (zero-copy NumPy arrays).
• CMake builds with -march=native for host-optimal SIMD codegen.

Health endpoint enhancements

• Version is now read from importlib.metadata (sourced from pyproject.toml) instead of hardcoding "1.0.0".
• Endpoint verifies database connectivity (SELECT 1) and storage directory existence.
• Response includes a checks map with per-component status/detail; overall status is "degraded" if any check fails.

Files changed (14 files, +585 −53)

File	Change
in_memory_cache.py	New — TTL cache with max-size eviction
cached_image_repository.py	New — Repository decorator
init.py	New — Package init
test_cached_repository.py	New — 16 tests for cache + decorator
postgres_image_repository.py	stream_scalars for list queries
health.py	DB/storage checks, dynamic version
image_schemas.py	ComponentCheck model, checks field
dependencies.py	Cache wiring, settings import
config.py	cache_ttl_seconds, cache_max_size settings
test_api.py	Updated health test with mock DB check
fast_resize.cpp	SSE2 SIMD, py::array_t I/O
CMakeLists.txt	-march=native
pyproject.toml	Version bump to 1.2.0
CHANGELOG.md	New [1.2.0] section

Validation

• ruff check src/ tests/ — all passed
• ruff format src/ tests/ — all formatted
• mypy src/ — 0 issues (43 files)
• pytest --cov=src — 46/46 passed, 80% coverage
• C++ module builds cleanly with -Wall -Wextra, runtime verified with RGB/RGBA arrays
• Clean Architecture dependency rule verified — no inward violations