My dashboard took 7.6 seconds to render fifteen numbers 🐌

Short summary

A real-world debugging story where a dashboard rendering fifteen numbers took 7.6 seconds due to three separate issues only visible at production data volume. Sentry tracing revealed the root cause after manually enabling MongoDB and Mongoose integrations, which are opt-in and not included in Sentry's default set. The author built a seed-and-benchmark harness to reproduce and measure fixes.

• •Sentry's default integrations exclude MongoDB/Mongoose spans — you must add them manually to see database queries in traces
• •Performance bugs that only manifest at production volume are the most dangerous because they ship unnoticed
• •A reproducible benchmark harness with seeded data is essential to verify fixes actually work

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