Session replay and trace correlation to debug OTP delivery

Description and use

Linking client‑side session replay with server‑side traces cut OTP delivery debugging from two days to seconds.

Problem

An OTP delivery bug was hard to diagnose because session replay and backend traces were not correlated, causing a two‑day investigation.

Outcome

By linking client‑side replay frames with server‑side trace IDs, the team cut debugging time from two days to seconds, enabling rapid resolution of OTP delivery issues.

Workflow

• 1. Install syncline-browser SDK in the front‑end and configure it with a key, endpoint, trace origins, release, and user ID.
• 2. Set OTEL_EXPORTER_OTLP_ENDPOINT on the server to point to Syncline.
• 3. Record a session; the SDK patches fetch/XHR to emit traceparent IDs as rrweb custom events.
• 4. In Syncline viewer, scrub the video; the tool maps player time to trace IDs and displays the corresponding span tree and SQL queries.
• 5. Identify the problematic request and its backend execution time instantly.

Evidence

Syncline plays the session recording, the backend trace, and the SQL that ran on one scrubber.

Source

The browser SDK records with rrweb and patches fetch and XHR to mint a W3C traceparent for every outgoing request.

Source