Fpm

Process manager modes pm=dynamic for most apps; pm=static only when workload is predictable and memory bounded. Key knobs: pm.max_children, pm.start_servers, pm.min_spare_servers, pm.max_spare_servers. Size max_children = (available RAM - OS/webserver/DB) / avg worker RSS. Opcache Enable: opcache.enable=1, opcache.enable_cli=0, opcache.memory_consumption sized for codebase, opcache.interned_strings_buffer, opcache.max_accelerated_files. Avoid opcache.revalidate_freq=0 in prod unless you control deploy restarts; prefer deploy-triggered reloads. Timeouts & queues Keep request_terminate_timeout sane (e.g., 30s-60s); long requests move to queues. Use pm.max_requests to recycle leaky workers (e.g., 500-2000). Watch slowlog to catch blocking I/O or heavy CPU. Observability Export status_path and scrape: active/idle/slow requests, max children reached. Correlate with Nginx/Apache logs for upstream latency and 502/504s. Alert on max children reached, slowlog entries, and rising worker RSS. Checklist Pool sizing validated under load test. Opcache enabled and sized; reload on deploy. Timeouts/queues tuned; slowlog on. Status endpoint protected and scraped.