Diagnose: Sentry SDK slowing the app down

# Diagnose: Sentry SDK slowing the app down

## Where the overhead comes from

1. **Trace volume.** Every sampled transaction builds spans in memory and ships them. At high sample rates on a hot path, this is the dominant cost.
2. **beforeSend work.** Your callback runs synchronously on every event. JSON parsing, regex scans, or network calls in `beforeSend`/`before_send` add latency to the request that errored.
3. **Breadcrumb capture.** The logging integration records breadcrumbs per log call. At `max_breadcrumbs = 50` default this is cheap; with verbose framework logging it adds up.

## Measure before tuning

Disable the SDK in one canary instance (empty DSN) and compare p99 latency and throughput against an identical instance with it on. If there is no measurable difference, the SDK is not your problem; do not tune blindly.

## The knobs, in impact order

1. Lower the trace sample rate, or switch to `traces_sampler` and return 0 for hot low-value routes (health checks, static assets).
2. Make `beforeSend` cheap: simple field deletes, no parsing, no I/O. Move heavy redaction to server-side scrubbing.
3. Reduce `max_breadcrumbs` or raise noisy loggers' levels instead of capturing everything.
4. For short-lived processes, check `shutdown_timeout`: too high blocks shutdown on network trouble, too low drops events.

## Verify

Re-run the canary comparison after tuning: the gap should close to noise. Also confirm the Usage stats show the expected drop in the tuned category, so the performance fix and the quota fix arrive together.