An API migration can mean changing platforms, moving infrastructure or shifting from a centralised to a distributed architecture. The process depends on interfaces, clients and operational requirements. Successfully transferring configuration does not, by itself, establish that the target platform behaves as expected.

1. Inventory interfaces and dependencies

List APIs, versions, endpoints, consuming applications, business owners and technical operators. Add data flows, protection requirements, traffic volumes and known exceptions. Include infrequent clients and older versions: an incomplete inventory is itself a security risk [1]. An OpenAPI description helps record HTTP interface contracts [2], but does not replace usage data or verification of active routes and policies.

The result is a migration list with ownership, dependencies and priorities. Start with a manageable group of APIs that can exercise the proposed process before business-critical interfaces follow.

2. Define the target architecture and ownership

Decide where requests are processed and configurations managed. Central control can be combined with distributed gateways [3]. Consider network boundaries, latency, availability, data residency and team responsibilities. With solutions such as Tyk, Kong, Apigee or Axway, capabilities and operating models depend on the version and edition. Use the gateway comparison for an initial shortlist, then test decisive requirements in a bounded technical evaluation.

3. Check authentication, policies and clients

Translate security rules according to their intended behaviour. Check token issuers, audience, permissions, key rotation, certificate chains and mTLS where applicable. Current OAuth security recommendations provide a reference [4]. Existing tokens or API keys are not automatically portable between platforms.

Paths, headers, error responses, timeouts, rate limits and transformations can also affect clients. Record whether each difference requires a platform adjustment or a client change, together with its owner and deadline. Provision credentials through controlled secret management.

4. Test behaviour and control parallel operation

The test plan should cover successful requests, missing or invalid permissions, traffic peaks and backend failures. Compare responses, latency, error rates and logging. Agree acceptance criteria with the responsible teams before testing.

During parallel operation, selected clients or routes can move to the target incrementally. Mirrored traffic must not trigger unintended writes or duplicate transactions. Test data, personal information and secrets in logs need appropriate protection. Two active platforms also need an explicit rule for which configuration is authoritative and how changes reach both environments.

5. Prepare cutover and rollback

The cutover plan names the sequence, approver, communication channels and measurable stop conditions. Account for DNS caches, ongoing connections and the validity of existing credentials. Decide how long the old platform remains available and who can order a rollback.

Rehearse the return path. Reverting routing does not undo data changes already made. If the backend or data model changes as well, those changes require their own recovery plan. Confirm that the old environment can still serve the agreed traffic before relying on it as the fallback.

6. Hand over operations and retire the old estate

Handover includes monitored interfaces, alert ownership, runbooks, certificate rotation and documented responsibilities. Confirm with application teams that the intended clients have moved. Retire old routes, credentials and infrastructure only after the agreed observation period and acceptance. Update the inventory and documentation so that an unmanaged parallel estate is not left behind [1].

Key takeaway

A sound API migration has five verifiable outcomes: a known inventory, a justified target architecture, tested contracts and access rules, a rehearsed cutover plan and an accepted operational handover.

Sources

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ServiceAPI Management & SecurityAPI OperationsTyk, Kong or Azure APIM