Mechanism◆Article
In a service-based architecture, a single product screen commonly requires data from several separate services, each storing only its own data, so the caller issues one call per service and merges the responses in the structure the user interface needs — and this merging step, API composition, exists in every system where data is split across more than one service.
Introduces the API composition problem: a product screen needs four separate services (profile, orders, delivery status, recommendations), and the developer must merge their responses — a step that exists wherever data spans multiple services. ✦ AI generated
Author (unnamed) · ByteByteGo Newsletter · 2026-08-13 · original ↗
In a service-based architecture, a single product screen showing a user profile, that user's five most recent orders, the delivery status of each order, and a short list of recommendations requires data from four separate services. Each service stores only its own data, so none of the four services returns the full set on its own. In other words, the caller issues four separate calls, and merges the resulting four responses in the structure needed for the user interface. This merging step is API composition, and it exists in every system where data is split across more than one service.
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- ·A product screen needs data from four separate services
- ·None stores the full set, each returns only its own data
- ·Caller issues four calls, merges responses for the UI
- ·This merging is API composition
- ·API composition merges calls into the UI structure
- ·It exists in every multi-service system
- ·Required wherever data spans more than one service
- ·The developer does the merging manually
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explains mechanism → The code that merges responses can run on the client, on a server, at a CDN edge, or inside a service; and while putting a server between the app and the services adds a network hop, it usually reduces total load time because trading four expensive phone-to-server round trips for one expensive trip plus four cheap server-to-server trips is a large net saving.Author (unnamed) · ByteByteGo Newsletterextends → Latency is only the first tradeoff in choosing where the merge runs: the location also determines behavior when one service is unavailable, how much of the response can be cached, and which team must approve a change before the screen ships.Author (unnamed) · ByteByteGo Newsletter