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API Orchestration & Multi-Backend Aggregation

Call multiple backends in sequence or parallel, merge or transform responses, and expose a single API surface with visual workflows.

Practical use cases

Concrete ways teams use Zerq for this scenario.

  • Expose one “unified profile” API that calls three backends

    Clients call a single endpoint; the workflow calls user service, preferences service, and history service, then merges the responses into one JSON. If one backend is slow or fails, you can add a timeout and fallback in the workflow without changing the client or the backends.

  • Validate, enrich, then persist in one request

    A single client request triggers a workflow: validate the payload, call an enrichment service, then call a write API. Data from each step is available to the next. You change the order or add steps in the workflow UI instead of deploying new orchestration code.

  • Hide backend splits and versions behind one contract

    You have v1 and v2 backends or region-specific services. The workflow chooses which to call based on path, header, or partner, and returns a single response shape. Clients see one API; you can move traffic or add backends without breaking them.

Outcomes

  • Single API surface that hides backend complexity; clients get one contract.
  • Orchestration and aggregation without new microservices or app deployments.
  • Changes to backend order, fallbacks, or mapping done in the workflow UI with full audit.

How Zerq helps

  • Visual workflow builder: add HTTP/backend call nodes, conditional branches, and custom response nodes; reference data from previous steps (e.g. first call’s response as input to the second).
  • Conditional routing and branches: route by header, query, or body; branch on status codes or parsed JSON so different backends or paths run per request.
  • Custom response nodes: return fixed or dynamic payloads (e.g. merged JSON, error shapes); set status codes (200, 202, 4xx, 5xx) without hitting a backend.
  • Optional code node for one-off logic (transform, merge) when visual nodes are not enough; still within the same workflow and audit trail.
  • Full request/response logging and Prometheus metrics per workflow and step; trace multi-backend calls in one place.
For architects & evaluators (technical context, requirements)

Technical context

Many APIs need to aggregate data from several backends (legacy systems, microservices, third-party APIs) or orchestrate multi-step flows (validate → enrich → persist → notify). Doing this in application code creates tight coupling and duplicated logic. A workflow-native gateway can define steps visually: call backend A, use its response in step B, branch on status, and return a composed or transformed response—all without deploying new service code.

Technical requirements

  • Multi-step flows: call one or more backends and pass data between steps.
  • Conditional branching based on request (path, headers, body) or response (status, body fields).
  • Merge or transform responses (e.g. combine two JSON payloads, map fields) before returning to the client.
  • Single stable API contract for clients while backends change or are versioned.
  • Observability: trace which steps ran and how long; audit and logs for compliance.

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