Web Development

Cloudflare caches private API responses between users

Environment

Environment

Express API behind Cloudflare with JWT cookies.

What happens

What happens

A user occasionally receives profile JSON belonging to the previous requester.

What I have tried

What I have tried

Purged the cache and changed the frontend request cache option.

I would appreciate advice on how to identify the root cause without risking existing data or configuration.

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AI DIAGNOSTICS

Incident analysis

Updated 3w ago• Trouble ID

Most likely causes

The origin marks authenticated responses as publicly cacheable without varying on authorization. 74%
A recent software, firmware or configuration change is exposing an existing compatibility issue. 44%

Summary

The reported behaviour is consistent with the origin marks authenticated responses as publicly cacheable without varying on authorization. The safest next step is to verify that hypothesis with a reversible test before making permanent configuration changes.

Suggested Fixes

Verify the likely cause
Send Cache-Control private, no-store for user data, bypass CDN caching on authenticated routes and remove any broad cache rule.
Validate and monitor
Reproduce the issue once after the change, review relevant logs or metrics, and keep a rollback path until the system has remained stable.