Agent Tech Stack
The ten layers of a production agent stack — model access, gateway, orchestration, runtime, state, vector, queue, observability, evals, secrets — with the choice criterion for each, three fully costed reference stacks, and the four buy-vs-build calls that matter.
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After this section you can
- Name the ten layers of an agent stack and what each one is for in one sentence
- Choose within each layer using a single decision criterion instead of a feature matrix
- Map every layer onto AWS, GCP, Azure, or a no-big-three equivalent
- Cost a weekend prototype, a Series-A SaaS, and a regulated enterprise stack line by line
- Recognise the trigger that forces a jump to the next tier — and resist jumping early
- Defend the four buy-vs-build calls that actually matter
The Agent Production Tech Stack
Not a tool list — a decision document. Ten layers, the criterion that decides each one, and three reference stacks costed line by line.
“What’s your stack?” is the question you get from your CTO, your first platform hire, and every interviewer who wants to know whether you have shipped one of these. The bad answer is a list of nine product names. The good answer is ten layers, one sentence each about what the layer is for, one criterion that decides the choice, and the trigger that would make you change it. This section is built to be read in either direction: skim the plain-English lines to understand the map, or read the criteria to make real decisions. Every layer names the AWS, GCP, and Azure service that fills it — plus the option that avoids the big three entirely.
Nine out of ten agent systems in production are Postgres, one queue, one Redis, OpenTelemetry, a thin model gateway, and roughly 800 lines of your own orchestration code. The elaborate stacks are almost always a team that adopted a framework before they understood the problem, and is now debugging the framework instead of the agent. Treat every row below as guilty until proven necessary; the default column exists because it is usually right.
The one-screen answer
If you remember nothing else from this section, remember this table. It is a defensible production stack for the large majority of agent products, and every row is justified in detail below.