API Composition
API composition is a pattern where a composer layer calls multiple upstream services, then combines and transforms their results into a single response. It lets clients retrieve data owned by different systems, such as a CRM and a billing provider, through one request.
Technical Architecture & Deep-Dive
In distributed systems, data is spread across services and SaaS tools. API composition implements cross-service queries in memory: the composer fetches each source, joins records by shared keys, and maps the merged result into the shape the client needs.
Running the composer at the edge keeps latency low because upstream calls execute in parallel from a well-connected network location. Declarative composition tools let teams define steps and output mappings without writing and hosting custom glue servers.
Key Architectural Benefits
Compose APIs Visually
Define upstream steps and output mappings, then deploy a composed endpoint globally.
Frequently Asked Questions
Q:How is API composition different from API aggregation?
The terms overlap. Aggregation emphasizes bundling multiple calls into one request, while composition emphasizes joining and reshaping the combined data into a new unified model.
Related Architecture Concepts
API Aggregation is the process of combining multiple distinct API calls into a single unified HTTP request. An intermediate edge gateway queries multiple upstream services in parallel, merges the returned data, and delivers a consolidated response to the client, drastically reducing mobile latency and network overhead.
Upstream Fan-out is an execution strategy where an edge gateway dispatches multiple HTTP subrequests to separate origin services concurrently rather than sequentially. The total latency is bound by the single slowest subrequest (max time) rather than the cumulative sum of all subrequests.
Response mapping is defining how fields from one or more upstream API responses are selected, renamed, and placed into a new output structure. Each mapping rule connects a source path, such as customer.email from a billing step, to a target path in the client response.
API orchestration is the coordination of multiple API calls in a defined sequence, where outputs from one step feed inputs to the next. An orchestrator manages ordering, dependencies, error handling, and the final response, so clients trigger a multi-step workflow with a single request.
Ready-to-Use Edge Recipes
To solve api composition tool for low code apps, never execute unauthenticated requests or embed private tokens directly in client bundles. RealComposer acts as a sub-10ms edge gateway running on Cloudflare Workers that securely injects credentials from your Secret Vault, normalizes responses, and prevents unauthorized API usage. Route calls through your RealComposer edge URL to guarantee complete privacy, robust origin validation, and low mobile latency.
Static HTML / Jamstack apps hit CORS and credential limits when calling Salesforce. Wire Salesforce REST from static sites with vault injection and no Express server. Use one RealComposer edge URL with OPTIONS handling, client tokens, and vault injection.
To merge salesforce contacts with hubspot crm one api, use one RealComposer pipeline with parallel steps. Parallel fetch Salesforce Contact and HubSpot CRM contact into one JSON object. Your Frontend / Web app makes one request instead of several sequential upstream calls.