Monitoring Endpoints

LoadFlux automatically captures metrics for every HTTP request that passes through the middleware.

What gets captured

For each request, LoadFlux records:

Metric	Description
method	HTTP method (GET, POST, etc.)
path	Route pattern (e.g., /api/users/:id)
statusCode	Response status code
durationMs	Request duration in milliseconds (nanosecond precision)
responseBytes	Response body size from Content-Length header
timestamp	When the request occurred

Route normalization

LoadFlux groups requests by route pattern, not by URL:

• Express: Uses req.route.path (e.g., /api/users/:id)
• Fastify: Uses request.routeOptions.url (e.g., /api/users/:id)

This means /api/users/1, /api/users/2, and /api/users/999 all appear as a single /api/users/:id entry in the dashboard.

Aggregation

Raw request data is buffered in memory and flushed to the database every 5 seconds (configurable via collection.aggregationWindow). During each flush, LoadFlux computes:

• Request count and error count
• Latency percentiles: p50, p90, p95, p99
• Min/max/avg duration
• Status code distribution: 2xx, 3xx, 4xx, 5xx counts
• Total response bytes

The buffer uses a swap pattern — a new buffer is created before the old one is flushed, so there's zero blocking on the hot path.

Slow requests

Requests exceeding the slowRequestThreshold (default: 500ms) are highlighted in the Endpoints page under "Slow Requests". You can adjust this threshold in code or from the Settings page in the dashboard.

Error tracking

Responses with status codes >= 400 are logged in the error log with:

• Timestamp, method, and path
• Status code
• Error message (from response body if available)
• Stack trace (if available)
• Request duration

View these in the Errors page of the dashboard.

Excluding routes

To exclude specific routes from monitoring:

app.use(loadflux({
  excludeRoutes: ["/health", "/ready", "/metrics"],
}));

Excluded routes won't appear in the dashboard or affect any metrics.

Performance

The middleware adds < 0.5ms overhead per request:

• Express: Uses process.hrtime.bigint() for nanosecond timing, captures metrics in the res.finish event
• Fastify: Uses Fastify's built-in reply.elapsedTime and the onResponse hook

LoadFlux's own routes (/loadflux/*) are not counted in metrics.