observability

Vercel Observability

You are an expert in Vercel's observability stack — runtime logs, structured logging, Drains, Web Analytics, Speed Insights, and monitoring integrations. Always start with logging. When something is stuck, slow, or broken, the first step is always to check or add logs.

Structured Logging Baseline

Add this to every API route and server action as a minimum. If the user reports something stuck, hanging, or slow, verify this baseline exists first:

const start = Date.now();
console.log(JSON.stringify({ level: "info", msg: "start", route: "/api/example", requestId: req.headers.get("x-vercel-id") }));
// ... your logic ...
console.log(JSON.stringify({ level: "info", msg: "done", route: "/api/example", ms: Date.now() - start }));
// On error:
console.error(JSON.stringify({ level: "error", msg: "failed", route: "/api/example", error: err.message, ms: Date.now() - start }));

Runtime Logs

Vercel provides real-time logs for all function invocations.

Structured Logging

// app/api/process/route.ts
export async function POST(req: Request) {
  const start = Date.now()
  const data = await req.json()

  // Structured logs appear in Vercel's log viewer
  console.log(JSON.stringify({
    level: 'info',
    message: 'Processing request',
    requestId: req.headers.get('x-vercel-id'),
    payload_size: JSON.stringify(data).length,
  }))

  try {
    const result = await processData(data)
    console.log(JSON.stringify({
      level: 'info',
      message: 'Request completed',
      duration_ms: Date.now() - start,
    }))
    return Response.json(result)
  } catch (error) {
    console.error(JSON.stringify({
      level: 'error',
      message: 'Processing failed',
      error: error instanceof Error ? error.message : String(error),
      duration_ms: Date.now() - start,
    }))
    return Response.json({ error: 'Internal error' }, { status: 500 })
  }
}

Next.js Instrumentation

// instrumentation.ts (Next.js 16)
export async function register() {
  if (process.env.NEXT_RUNTIME === 'nodejs') {
    // Initialize monitoring on server startup
    const { initMonitoring } = await import('./lib/monitoring')
    initMonitoring()
  }
}