Client-Side Microservices Architecture (CSMA)
June 2023 · Enrico Piovesan
This is where the thinking started.
The browser kept getting treated as a consumer of server logic rather than a legitimate execution environment in its own right. Every decision that could be made locally was deferred to a round trip. Every business rule that could run in the browser was reimplemented on the server because that was where logic was supposed to live. The frontend was a rendering layer. It was not supposed to think.
That assumption made less sense every year. Browsers got faster. WASM made native-speed execution possible. Offline requirements became real. AI changed what clients needed to do. And yet the architecture stayed the same: server decides, browser displays.
CSMA was an attempt to write down why that assumption was wrong and what the alternative looked like.
What the paper covers
The browser as a runtime. The central argument is that the browser is a legitimate execution environment and should be treated as one architecturally. That means business logic that runs locally, not logic that is fetched and rendered.
Service-oriented thinking applied to the frontend. CSMA applies the same modularity principles that made backend microservices successful to the client side. Each capability is a self-contained unit with declared inputs, outputs, and contracts. Not a component tied to a framework.
Stateful and stateless services. The paper distinguishes between capabilities that manage their own state and capabilities that are pure functions. Both have a place in a client-side service architecture. The distinction matters for lifecycle management and composition.
Isolation and boundaries. How client-side services communicate without coupling. The event bus pattern, capability boundaries, and the contract layer that keeps services composable as the system grows.
The portability seed. CSMA was the first time I wrote down a pattern I had been circling around for years. The question it left open (why stop at the browser?) became the question that UMA answered.
Who it is for
Frontend architects and senior engineers building complex client applications who are hitting the limits of component-based thinking and want a more disciplined model for managing logic at the client layer.
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