How I scaled a TikTok Ads automation SaaS to 7M requests/day as a solo dev

A friend in the tech group asked me how I handled observability and security. I answered, the conversation drifted to stack choice, then to why not Kubernetes, then to when it's worth breaking up the monolith. He suggested I write about it. So here it goes. The context I run a SaaS that automates TikTok Ads campaign management for agencies. Each customer has N Business Centers → N Advertiser Accounts → N Campaigns → N Ad Groups → N Ads. Today's numbers: R$ 87k in MRR R$ 1M in ARR More than 7 mil