Set up log aggregation

Set up centralised log aggregation for [Number] services running in [Environment, e.g. Kubernetes, Docker Compose]. Use [ELK Stack / Loki + Grafana / Datadog] as the backend. Configure each application to emit structured JSON logs with consistent fields including service name, log level, trace ID, and timestamp. Set up a log shipper such as Filebeat, Promtail, or a cloud agent, create a saved search for [Error pattern], and define a log retention policy with different durations for debug and error levels.