AWS X-Ray

Distributed tracing service that follows a single request across every service it touches.

Verified against AWS documentation · 2026-08-27

Key facts

01Traces a request end-to-end: segments (per service) and subsegments (per downstream call) stitched into one trace
02Service map auto-draws your architecture from trace data — latency, errors, and throttles per node
03Sampling by default: first request each second + 5% of the rest, so you're not paying to trace everything
04Limits: 500 KB max trace size, 30-day trace retention, annotations are indexed/searchable but metadata is not

Phrases and scenarios that point here.

"Trace requests across microservices", "find the bottleneck", "end-to-end latency" → X-Ray
"Which service in the chain is causing errors" → service map
Debugging Lambda or API Gateway latency across multiple hops → enable active tracing
Filter traces by business attribute (user ID, order ID) → annotations

01A checkout request passes through API Gateway → Lambda → DynamoDB → SQS and takes 4 seconds; X-Ray shows the 3.5s is one throttled DynamoDB call, not the Lambda code
02New microservice deployed Friday; the service map lights up a node red Monday morning — you see the failing dependency without grepping a single log
03Tagging traces with an annotation like orderId so support can pull the exact trace for one customer's failed order
04Comparing p50 vs p99 latency per downstream hop to prove which team's service is dragging the SLA

01Billed on three dimensions: traces recorded, traces retrieved, traces scanned — recording costs ~10x more than retrieval/scanning
02Sampling is your cost lever: default sampling means bursty traffic doesn't linearly inflate the bill
03Perpetual free tier: 100,000 traces recorded + 1,000,000 retrieved/scanned per month
0430-day trace storage included — no separate storage charge
05X-Ray Insights, if enabled, bills per trace processed on top of recording