Observability is the ability to answer arbitrary questions about a production system from its external outputs — without shipping new code. It rests on three pillars: logs (discrete events), metrics (aggregated numbers over time), and traces (request paths across services).
Modern observability adds OpenTelemetry (the vendor-neutral instrumentation standard) and structured event data. Leading platforms in 2026: Datadog (enterprise), Honeycomb (event-based, developer-loved), New Relic, Grafana Cloud, Sentry (errors and performance), and open-source stacks (Loki + Prometheus + Tempo + Grafana).
Good observability lets you diagnose incidents in minutes instead of hours. Bad observability means you find out about problems from customers. Nagro Solutions ships Sentry error tracking on every project and richer observability (Datadog, Honeycomb) on systems where downtime cost justifies the investment.