performance

OFFSET gets slower as tables grow and becomes inconsistent under writes. Keyset pagination is stable and fast: paginate by (created_at, id) cursor. This is a common “senior Rails” upgrade for activity feeds.

Most ‘caching’ bugs are really invalidation bugs, so I stick to a simple cache-aside pattern with conservative TTLs and treat cache misses as normal. The big failure mode to avoid is a stampede: if many requests miss at once, you can crush your DB. Fo

Backfills often fail because we accidentally load full records and associations. Use select to fetch only needed columns and find_each to keep memory flat. This is basic, but it’s where outages come from.

Heavy work inside a transaction increases lock time and deadlock risk. Use after_save_commit to schedule slow tasks (thumb generation, external sync) once the write is durable.

ETags are a simple high-impact performance lever: they reduce bandwidth and controller CPU. Use stale? with a stable ETag component list and last_modified so intermediary caches and browsers can do conditional GET.

In containerized environments, the Go runtime can benefit from knowing the memory budget. With Go 1.19+, debug.SetMemoryLimit lets you set a soft limit so the GC reacts more aggressively before the process gets killed by the OOM killer. I treat this a

Rayon makes data parallelism trivial: replace .iter() with .par_iter(), and your loop runs in parallel across all CPU cores. It uses a work-stealing scheduler to balance load automatically. I use rayon for CPU-bound tasks like image processing, data t

Query debugging identifies performance and correctness issues. I use EXPLAIN ANALYZE to understand execution plans. Slow query logs reveal problematic queries. pgstatstatements tracks query statistics. Understanding sequential scans vs index scans hel

Unnecessary re-renders hurt performance, especially with expensive computations or callbacks passed to child components. useMemo memoizes computed values, recalculating only when dependencies change. useCallback memoizes function instances, preventing

Instruments profiles iOS apps to identify performance bottlenecks, memory leaks, and energy issues. The Time Profiler instrument samples the call stack to show which functions consume CPU time. Allocations tracks memory usage and finds leaks by identi

The Intersection Observer API efficiently detects when elements enter/exit the viewport, enabling lazy loading, infinite scroll, and analytics without expensive scroll listeners. I create observers with thresholds defining when callbacks trigger—0.0 m

Bulk operations reduce database round-trips dramatically. I use bulk_create() for inserting many objects at once, bulk_update() for updates, and update() for queryset-level updates. These bypass save() methods and signals for speed. For large datasets