System Design 101: Scaling from 0 to 1 Million Users

Scaling Path Summary

1. Single Host: App server and Database on the same machine (good for development).
2. Database Separation: Separate the app tier from the database tier.
3. Horizontal Scaling: Introduce a Load Balancer (Nginx/HAProxy) and deploy multiple stateless app servers.
4. Read Replicas: Distribute DB reads by pointing them to read-only DB replicas while sending writes to the primary DB.
5. Caching: Place a cache layer (Redis/Memcached) in front of the DB to avoid expensive database reads.
6. CDN (Content Delivery Network): Serve static assets (images, CSS, JS) from edge servers close to users.
7. Database Sharding: Partition the database horizontally across multiple servers to handle higher write volume.