Why I Rewrote Four Services in Go

I had four small services. Each one was a Model Context Protocol adapter — a thin wrapper that lets an AI agent call out to some external thing. One talked to Replicate for image generation. One talked to a Nostr-friendly social poster. One was a Git-aware research helper. One was a Tavily-powered web search. They were all written in Python. They all ran on Knative on a small Kubernetes cluster. They all worked. And they were all just slightly too slow to use. A six-second cold start is fine for nothing. It is the precisely wrong amount of time — slow enough to be noticed, fast enough to feel almost loaded. An AI agent waiting six seconds for a single tool call does not know it is waiting for a cold start; it just knows the tool is sluggish. The user does not know either. The user just thinks the agent is broken. And six seconds was a good day. Some of the services took longer. So I rewrote them in Go. This is what that cost me, and what the measurements actually were before and after. The actual problem Cold starts on serverless platforms are an old problem with a well-known shape. The platform spins your container up only when traffic arrives, so the first request after an idle period pays the full startup tax — image pull (or warm cache hit), container start, language runtime initialisation, application bootstrap. For Python, application bootstrap is where the bill arrives. The interpreter has to start. import statements run. The dependency tree gets walked. If you have ever wondered why a hello world Flask app feels so much heavier than a hello world Go binary, this is why. Python is doing real work before your code runs. Go has already started. On a small Kubernetes cluster — small as in I am paying for it personally — you do not keep a fleet of warm replicas around. You scale-to-zero. You scale-to-zero because that is the entire point of using serverless on small infrastructure. The trade-off is that every idle service eats a cold start the next time it is inv