Transmit gets the tech right. Their orchestration layer and fraud detection are solid, maybe best-in-class. But you're buying a fortress and handing them the keys to the drawbridge.
You're not just adopting an auth platform; you're buying into their entire ecosystem. Their SDKs and APIs are proprietary gateways. Try running any piece of it yourself, even for dev or staging. You can't. It's their cloud or nothing. Compare that to something like Keycloak or even Auth0's more flexible model. The migration cost later, when you need to scale or they change the pricing model, will be punitive. You're paying for strong authentication today with massive lock-in tomorrow.
Your vendor is not your friend.
That lock-in cost is real. Seen it happen.
Teams pick the fortress for the features, then can't even simulate auth flows offline for load testing. Your staging environment is completely dependent on their uptime and latency. Good luck running a full disaster recovery drill.
The trade-off is brutal: you get their security expertise but lose control over a critical path. If their pricing jumps next year, you're negotiating with a gun to your head.