Teams often shop for an open API gateway the way they shop for a commercial one: they compare policy catalogs, plugin counts, dashboards, and analytics screens side by side. That checklist approach hides the one thing that actually determines how hard your migration will be, which is not how many features a gateway has but how much of your current platform is gateway at all. An open gateway replaces the data plane cleanly; the developer portal, analytics, and governance around it are a separate build. Confuse the two and you will either over-scope the project or discover the missing half mid-flight. The better method is to decide the few factors that genuinely change the answer, measure your real usage against them, and only then compare products. This guide gives you that rubric.
Start with the decision, not the gateway
Before you shortlist anything, separate what you run into two layers. There is the data-plane gateway that proxies and secures live traffic, and there is the control plane of developer portal, analytics, and governance wrapped around it. An open gateway replaces the first layer policy for policy. The second layer you assemble from open components: a portal, a metrics stack, GitOps for configuration. Write down which control-plane pieces you genuinely depend on versus merely have switched on, because that list, not the gateway feature comparison, is the real size of your job.
The factors that size the job
- Gateway or full platform. The decisive question. If you only need the data plane, an open gateway is close to a like-for-like swap. If you lean on the portal, analytics, and governance, budget for assembling open equivalents around the gateway.
- The MuleSoft integration trap. If you are leaving Anypoint, remember it is also an integration and ESB platform, not just a gateway. Moving the gateway to an open target does not replace your Mule flows. That integration logic is a separate concern on its own track, and treating the two as one migration is the most common way these projects fail.
- Configuration style. Decide whether you want declarative, GitOps-driven configuration or a database-backed, UI-managed control plane. The open gateways differ here, and matching this to how your team already works matters more than raw feature count.
- Plugin and policy needs. Inventory the policies you actually enforce (auth, quotas, rate limiting, transforms, custom callouts) and confirm each maps to an available plugin. Bespoke JavaScript or Java logic is where effort hides, so surface it early.
- Scale and traffic shape. Call volume, latency budget, and number of environments shape both the deployment topology and where costs land. Size the target for your real traffic, not a headline number.
- Support expectations. If you need a vendor to call, that argues for a commercially backed distribution of an open gateway rather than pure community software, and it changes the economics you should be modeling.
Which gateway suits which platform
Score your platform against the criteria, then use these as starting points. Kong Gateway OSS is the natural target when you are leaving Kong Enterprise, since Enterprise runs the same open-source core and the move is largely removing licensed features and substituting open equivalents. It also suits teams that want a mature plugin ecosystem and either declarative or database-backed configuration. Apache APISIX fits teams that want a fully declarative, GitOps-oriented gateway with a strong plugin set. Tyk suits teams that want an open gateway with an included dashboard and portal in its open distribution. Apigee, MuleSoft Anypoint, and Kong Enterprise are the sources you are leaving. The honest framing: any of these open gateways replaces the data plane well, but none hands you a finished control plane, so plan the portal and analytics as deliberate work rather than assuming it comes in the box.
Where API-gateway moves come apart
The most common error is scoping the project as “replace the platform” when what maps cleanly is only the gateway, leaving the portal and analytics as an unplanned surprise. The second, specific to MuleSoft, is bundling the integration and ESB migration into the gateway migration, which balloons the effort and risk. The third is choosing a gateway whose configuration model fights how your team works, so a technically capable tool becomes a daily friction. A quieter fourth: not getting a real renewal quote from the incumbent, so the comparison is against a guess rather than the number you are trying to beat.
Prove it API by API
Turn your top candidate into a pilot with written acceptance criteria. Stand the open gateway up alongside the incumbent, re-create services, routes, and policies for a first slice of APIs, put both behind DNS, and cut over one API at a time while watching authentication, rate-limit behavior, and latency. Keep consumer contracts stable so nothing downstream notices the swap. Model the savings with the tool at /calculator/ and treat the defaults as illustrative until you price your own infrastructure and support. Migrate by API, validate as you go, and retire the commercial platform only once every consumer has moved and, if you are leaving MuleSoft, only after the integration layer has been handled on its own track.