Scaling a system is an iterative process. Iterating on what we have learned in this chapter could get us far. More fine-tuning and new strategies are needed to scale beyond millions of users. For example, you might need to optimize your system and decouple the system to even smaller services. All the techniques learned in this chapter should provide a good foundation to tackle new challenges. To conclude this chapter, we provide a summary of how we scale our system to support millions of users:

Keep web tier stateless

Build redundancy at every tier

Cache data as much as you can

Support multiple data centers

Host static assets in CDN

Scale your data tier by sharding

Split tiers into individual services

Monitor your system and use automation tools

Congratulations on getting this far! Now give yourself a pat on the back. Good job!