How to scale your server software, TLDR version:
0. Start with a monolith and one tiny server until you have actual paying clients. Then upgrade to two tiny app servers (load balancing or failover depending on the app) and a database server if needed.
1. Update to faster servers. Repeat until there's nothing faster on the market.
2. Rent another server. Repeat until your CFO is looking at you funny.
3. Pay someone experienced to tell you how inefficient your software is. Fix it and go back to step 2.
The astute reader will notice that none of that includes Kubernetes, Kafka, gRPC, autoscaling, nosql, microservices… You are welcome.
Feel free to contact me for part 3.