Understanding microfrontend types in real systems

Microfrontends sound great in theory. Independent teams, faster deployments, tech flexibility. But the magic (and the headaches) truly begins when you have to stitch all these separate pieces together into a cohesive app. The key decision isn't just "Should we use microfrontends?" It's "Where and how does the composition happen?"

There are different strategies for gluing together separate, independently developed frontend pieces. You'll hear these composition strategies referred to in three common ways: build-time integration, runtime integration, and the Single-SPA approach. These aren't rival hype terms fighting for attention. Each strategy comes with its own real-world trade-offs in deployment, performance, team independence, and operational headaches (like debugging and ownership). Let’s take a detailed look at these microfrontend types.

Microfrontend types and integration strategy

At a technical level, microfrontend types differ primarily in how JavaScript, CSS, and application state are composed within a microfrontend architecture. This choice affects deployment independence, dependency management, caching behavior, performance characteristics, and failure isolation. Teams often underestimate this and treat microfrontends as a UI concern. These are system-level decisions that surface in CI pipelines, CDN strategies, and incident response.

Runtime microfrontends

Runtime microfrontends compose applications in the browser at runtime, making this microfrontend type ideal for independent deployment and high team autonomy. Individual microfrontends are built and deployed independently and loaded dynamically at runtime, typically through mechanisms such as dynamic imports, Webpack Module Federation, or a custom app shell. The host application is responsible for resolving remote entry points, loading bundles, and coordinating shared dependencies like React or design system libraries. In one system I worked on, teams shipped independently through runtime composition, but even minor mismatches in shared dependency versions surfaced as runtime errors rather than build failures, forcing us to introduce strict version contracts and shared dependency policies.

• Why it shines: Runtime microfrontends work exceptionally well for high-velocity teams. Independent deployments allow features to reach production without waiting on coordinated releases, which becomes critical as the team count grows.
• The edge: They offer the highest degree of deployment independence and flexibility, especially in heterogeneous environments where teams evolve at different speeds or use different tooling.
• The challenge: Because integration occurs in the browser, version drift can cause runtime failures. This makes observability, load failure handling, and disciplined shared state management non-negotiable if you want to avoid hidden coupling.

Build-time microfrontends

Build-time microfrontends integrate individual modules during the build process, producing a single deployable artifact within a microfrontend architecture. Teams still develop features in isolation, often as separate packages or repositories, but composition happens in CI rather than in the browser. This is commonly implemented using monorepos, shared build pipelines, or package-based integration where microfrontends are versioned and consumed as dependencies. In one case, moving latency-sensitive flows to build-time integration eliminated a class of runtime failures and made performance characteristics far more predictable.

• Why it shines: Build-time integration excels in systems where stability and performance matter more than raw deployment speed. Catching dependency conflicts during CI significantly reduces production surprises.
• The edge: It provides predictable runtime behavior and enables deeper performance optimizations through bundling and tree-shaking.
• The challenge: Reduced deployment independence. Teams must coordinate releases, and changes in one module can require a full rebuild, placing more pressure on versioning discipline and release processes.

Single-SPA microfrontends

Single-SPA microfrontends rely on Single-SPA as an orchestration framework rather than a composition strategy by itself. It provides a runtime layer that registers multiple microfrontend applications and controls their lifecycle based on routing and application state. Each microfrontend exposes standardized lifecycle methods for bootstrap, mount, and unmount, while a root configuration determines when those lifecycles are triggered. During a phased migration of a legacy frontend, Single-SPA allowed new applications to be introduced incrementally while keeping the existing system operational, avoiding a full rewrite.

• Why it shines: Single-SPA is particularly effective during platform transitions. It enables incremental modernization while keeping legacy systems live, which is often the only viable path for large products.
• The edge: It allows multiple frameworks to coexist under a single routing and lifecycle model, giving teams flexibility without forcing immediate rewrites.
• The challenge: Without strong conventions, complexity shifts to orchestration. Shared state, routing consistency, and cross-application communication must be designed deliberately to avoid recreating tight coupling at the root level.

Real-world trade-offs

Runtime, Build-Time, and single-SPA microfrontends solve different problems. Runtime composition optimizes for independent deployment and team autonomy. Build-time composition optimizes for stability, performance, and predictability. Single-SPA optimizes for controlled evolution in complex or transitional systems. None of these approaches is universally correct. The right choice depends on how much operational complexity your organization can absorb and where you want failures to surface.

Choosing the right microfrontend approach

Microfrontend types are architectural tools in modern frontend architecture, not ideology. Choosing between Runtime, Build-Time, and single-SPA ultimately comes down to where you want integration risk to reside and how much coordination your teams can sustain. The next blogs in this series will dive into each approach in depth, covering concrete implementation patterns, tooling choices, and hard-earned lessons from production systems. Microfrontends succeed when technical decisions reflect organizational reality rather than architectural fashion. If you need help with microfrontends, Opcito’s experts can help. Reach out to us at contact@opcito.com to talk to an expert.