What is New Relic?

New Relic is a commercial SaaS observability platform. Language agents (Java, .NET, Node.js, Python, Ruby, PHP, Go) instrument web transactions, outbound HTTP calls and database queries; infrastructure agents, log forwarding, synthetic monitors and an OpenTelemetry (OTLP) endpoint feed the same account. All of it is stored as events and queried with NRQL, New Relic’s SQL-like query language. Pricing is based on data ingested and on user seats, with a free tier that includes 100 GB of ingest per month and one full platform user.

Why use it in the API Lifecycle?

Transaction-level APM: Each web transaction is named after the route or controller, with throughput, response time, error rate and Apdex, plus traces of slow requests.
Distributed tracing: Agents support W3C Trace Context (traceparent and tracestate) and can still send the older proprietary newrelic header; W3C-capable agents prefer traceparent when both arrive.
OpenTelemetry ingest: Services instrumented with OpenTelemetry can export directly over OTLP to New Relic, so you are not tied to its agents.
NRQL: Ad hoc queries and alert conditions can be written over transactions, spans, logs and metrics, for example the p95 duration of one route, faceted by status code.
Synthetic monitoring: Scripted API monitors call endpoints on a schedule from managed or private locations and alert on failures.

Best Practices

Make sure transactions are named by route template, not by full URL. A transaction name per resource ID creates thousands of names, hits the agent’s naming limits and makes per-endpoint metrics meaningless.
Build alerts on rates, not counts: the error percentage and p95 or p99 duration per key transaction, over a window long enough to ignore single slow requests. A count of errors rises with traffic and pages you for a busy day.
Separate client errors from server errors. Track 4xx and 5xx per route independently; a surge of 401 Unauthorized after a client release is a different incident from a surge of 500 Internal Server Error, and only the second is the API team’s fault.
Propagate W3C traceparent through every proxy and queue, and turn off the proprietary header once all services understand W3C, so traces join with OpenTelemetry-instrumented services. Agents use adaptive head-based sampling by default; use Infinite Tracing (tail-based) if you need to keep every slow or failed trace. See Observability and Tracing.
Keep request parameters, headers and bodies out of captured attributes unless you need them, and use the agent’s attribute include and exclude configuration to drop anything sensitive. Never capture Authorization or Cookie. Logging and PII covers redaction.
Watch ingest. Billing is per GB, so verbose logs and high-cardinality custom attributes are what drive cost; drop or sample noisy data at the source rather than paying to store it.