I’ve been back in the trenches of finance and technology. Fintech, in practice, is rarely one company owning the whole stack. It is a chain of regulated firms packaging compliance-heavy services and reselling them as APIs to the next layer of financial systems. Those systems integrate, wrap, and sell again. A few major players sit near the top, wired into banks, blockchains, or DeFi protocols. Everyone else hangs off those rails.
That model only works if the rails are safe to build against. Lately I’ve been watching a gap that keeps showing up: a lot of fintech APIs are live-only. There is no sandbox. No isolated environment that behaves like production without touching real money, real customers, or real settlement.
This is not unique to fintech. Insurance has the same problem. As a developer you get handed production credentials out of the box. Your staging environment is already broken for that path, because you cannot point the team’s shared config at a live integration and call it “safe.” One wrong request, one shared secret in the wrong place, one webhook firing into the wrong environment, and you are past the point where “we’ll just be careful” is a real control.
That is a bottleneck for building enterprise financial rails.
So teams do what they always do when a vendor leaves a hole. Some invent the missing piece. They stand up mocks. They stub responses. They maintain a fake version of the partner’s API that drifts the moment the real one changes a field, a status, or a webhook shape. The integration looks green in CI and still fails the first time it meets production.
Others do not mock at all. In startup environments, speed is the product. Spending weeks rebuilding someone else’s API in miniature feels like wasted engineering time. So they skip it. They wire staging to live, or they leave that path untested until launch day. That is not recklessness for its own sake. It is a rational response to missing infrastructure.
I try to mock. When a partner has no sandbox, I build a stand-in so the team can keep shipping without pointing every environment at production. It helps. It keeps the rest of the system movable. It is also a bandage.
Mocks are local insurance against a vendor gap. They are not a substitute for a real sandbox. They drift. They under-simulate settlement, compliance edges, and failure modes. They burn time that should have been product time. Every mock you maintain is evidence that the rail you depend on was incomplete.
Sandbox is not a nice-to-have for this industry. It is part of the product. If you sell financial infrastructure, you should ship:
A sandbox that mirrors production behavior, including errors and edge cases
Separate credentials and signing keys from live
A clear mode switch so staging cannot accidentally become production
Webhooks and settlement flows that can be exercised end to end without real funds
Until that is normal, integrators will keep paying the same tax: mock systems for the careful teams, live risk for the fast ones, and delayed confidence in the one path that actually moves money.
Financial rails are only as strong as the environments people are allowed to test them in. Live APIs without sandboxes force builders to choose between speed and safety. That should not be the default. Mocking is what we do in the meantime. It should not be the industry’s answer forever.
