Millions of users and beyond

Scaling is an endless journey. As you grow past millions of users you may also split the system into smaller services (decoupling). But this checklist already takes you a long way:

• ✅ Web servers hold no session state (stateless); sessions live in a shared store
• ✅ Every layer has a spare (redundancy), so no single machine can take the site down
• ✅ Hot data is served from a cache, not the database
• ✅ The site runs in more than one data center
• ✅ Images, JS and CSS come from a CDN
• ✅ The database is sharded once one server can't hold it
• ✅ Big tiers are broken into separate services that scale on their own
• ✅ Everything is monitored, and builds, tests and deploys are automated

Press play to watch the full architecture assemble itself, one piece at a time.