Zero-downtime deployments: Best practices and patterns

The Importance of Zero-Downtime Deployments

In today's always-on world, even a few minutes of downtime can cost your business thousands of dollars and damage customer trust. Zero-downtime deployments ensure your application remains available while you roll out updates.

Deployment Strategies

Blue-Green Deployment

Maintain two identical production environments. Deploy to the inactive environment, test it, then switch traffic over instantly.

cupadev deploy --strategy blue-green

Rolling Deployment

Gradually replace old versions with new ones, updating a few instances at a time. This reduces risk and allows for quick rollback if issues arise.

Canary Deployment

Roll out changes to a small subset of users first. Monitor for issues before gradually increasing the rollout percentage.

Database Migrations

Database changes are often the trickiest part of zero-downtime deployments. Key principles:

• Make changes backward-compatible
• Deploy schema changes separately from code changes
• Use feature flags to control new functionality
• Never drop columns or tables in the same release as code changes

Health Checks and Monitoring

Implement robust health checks so CupaDev can verify your application is ready before routing traffic:

// health.js
export default function handler(req, res) {
  // Check database connection
  // Check external services
  // Return 200 only if all systems are operational
  res.status(200).json({ status: 'healthy' });
}

Rollback Strategy

Always have a rollback plan. With CupaDev, rolling back is instant:

cupadev rollback --to-version previous

Conclusion

Zero-downtime deployments are essential for modern applications. By combining proper deployment strategies, careful database migration practices, and robust monitoring, you can deploy confidently without impacting your users.