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Overview

PyqDeck uses a three-layer observability stack: Sentry for error tracking and profiling, Better Stack (Logtail) for structured logging, and Better Uptime for availability monitoring.

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Error Tracking: Sentry

Packages: @sentry/node v10, @sentry/profiling-node v10

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Initialization

Sentry is initialized in the backend entry point (backend/src/index.js): 
import * as Sentry from "@sentry/node";
import { nodeProfilingIntegration } from "@sentry/profiling-node";

if (process.env.SENTRY_DSN) {
  Sentry.init({
    dsn: process.env.SENTRY_DSN,
    environment: config.nodeEnv,
    integrations: [nodeProfilingIntegration()],
    tracesSampleRate: 1.0, // 100% of transactions
    profilesSampleRate: 1.0, // Profiling for all traces
  });
}

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What’s Captured

FeatureSettingImpact
Error trackingAll 500+ errorsCaptured via Sentry.captureException(err)
Performance tracestracesSampleRate: 1.0100% of requests traced
CPU profilingprofilesSampleRate: 1.0CPU profiles attached to traces
Environment taggingenvironment: config.nodeEnvSeparates dev/staging/production

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Error Handler Middleware

All server errors flow through the error handler (backend/src/middlewares/errorHandler.js): 
import * as Sentry from "@sentry/node";

export const errorHandler = (err, req, res, next) => {
  // Report to Sentry
  if (err.statusCode >= 500) {
    Sentry.captureException(err);
  }

  // Log locally
  logger.error(err.message, {
    stack: err.stack,
    path: req.path,
    method: req.method,
  });

  // Send response (strip stack in production)
  res.status(err.statusCode || 500).json({
    success: false,
    error: {
      message:
        config.nodeEnv === "production" && err.statusCode >= 500
          ? "Internal server error"
          : err.message,
    },
  });
};
Sentry also sets up Express error handling via Sentry.setupExpressErrorHandler(app) in app.js.

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Logging: Winston + Better Stack

Packages: winston, @logtail/node, @logtail/winston

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Three Transport Layers

The logger (backend/src/utils/logger/index.js) sends logs to three destinations:
TransportFormatRetentionPurpose
ConsoleColorized, timestamped (YYYY-MM-DD HH:mm:ss)N/ALocal development
Daily Rotating FileJSON, logs/application-YYYY-MM-DD.log14 days, 20MB max per fileLocal archive
Logtail (Better Stack)JSON, structuredConfigurable in Better StackProduction monitoring

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Logtail Configuration

Logtail is enabled when LOGTAIL_SOURCE_TOKEN is set: 
import { Logtail } from "@logtail/node";
import { LogtailTransport } from "@logtail/winston";

if (process.env.LOGTAIL_SOURCE_TOKEN) {
  const logtail = new Logtail(process.env.LOGTAIL_SOURCE_TOKEN);
  transports.push(new LogtailTransport(logtail));
}
On startup, the system logs: "System initialized and connected to Better Stack!"

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HTTP Request Logging

Morgan middleware logs all HTTP requests in 'dev' format: 
GET /api/v1/papers 200 45.2ms
POST /api/v1/bookmarks 201 12.8ms

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Availability Monitoring: Better Uptime

URL: pyqdeck.betteruptime.com Better Uptime monitors the health endpoint: 
GET /api/v1/health
If the endpoint is unreachable or returns a non-200 status, Better Uptime sends alerts to the team.

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Rate Limiting

File: backend/src/middlewares/rateLimiter.middleware.js
  • Store: In-memory TTL (not Redis)
  • Default: 100 requests per 15-minute window
  • Configurable via RATE_LIMIT_WINDOW_MS and RATE_LIMIT_MAX env vars
Rate limit exceeded responses include standard headers: 
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 0
X-RateLimit-Reset: 1620000000

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Health Endpoints

EndpointDescription
/api/v1/healthSimple health check (used by Better Uptime and Render)
/api/v1/health/detailedDetailed health including database connection status

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Debugging Production Issues

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Step 1: Check Better Uptime

If the service is down, Better Uptime will show the outage and when it started.

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Step 2: Check Sentry

For application errors:
  1. Open the Sentry dashboard
  2. Filter by environment (production)
  3. Check the error’s transaction trace for the full request lifecycle
  4. View the attached CPU profile to identify performance bottlenecks

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Step 3: Check Better Stack

For structured log analysis:
  1. Open the Better Stack dashboard
  2. Search logs by user ID, request path, or error message
  3. Correlate with Sentry events using timestamps

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Step 4: Check Render Logs

For deployment and infrastructure issues:
  1. Open the Render dashboard
  2. View the service logs for startup errors, crash loops, or deployment failures

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Security Considerations

  • Stack traces are stripped in production for 500-level errors
  • CLERK_SECRET_KEY is never logged or exposed
  • Rate limiting prevents abuse
  • Non-root Docker user limits container escape risk

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Next Steps