The queue, the cache, the search index, the vector store, the job scheduler and the analytics table for a product with 40,000 daily users all live in one Postgres 18 instance, and that was the plan from the start. Here's what each piece looks like, what it costs, and the three specific signals that would make me move one of them out.
A model provider had a bad Tuesday, and our summarisation feature spent four hours returning empty strings to customers because nothing between the API and the user knew what to do with a 529. The feature now has a kill switch, a fallback, a budget and a canary. Without those four it was a demo.
Node 24 ships TypeScript, a test runner, fetch, a permission model and a single-file executable builder. Bun is faster at almost everything and now has a company with deep pockets behind it. Deno has the cleanest security story. I run all three in production, and the answer to 'which one' is different for each of my four services, for reasons that have little to do with benchmarks.
Python 3.14 made the no-GIL build officially supported, and the single-thread penalty fell from 40 percent to single digits. I moved a CPU heavy ingestion service across. The 3x speedup on the hot path was real, and so were three bugs that only exist without the lock. Tests caught none of them.