Look first at proven experience, not the length of the client list. Request three or four projects that sit close to your stack, and then ask specifically which engineers actually built it. An honest provider is happy to connect you with the people who would work on your project. Vague answers at this stage almost always mean you are talking to a reseller.
The agreement deserves more scrutiny than the proposal. Three sections matter more than the rest: assignment of intellectual property, confidentiality, minimum viable product development company and termination and handover. Every artifact must transfer to you as it is paid for, together with documentation, pipelines and deployment scripts. Watch for any clause that leaves reusable components with the vendor, as it is usually the dependency that makes switching painful.
Ask where their numbers come from. A serious estimate arrives with a written set of assumptions, a task-level breakdown and software architecture consulting a range rather than a single number. A fixed-bid deal only makes sense when the scope is genuinely frozen; in any other case the provider pads the number and you pay for it anyway. A time-and-materials model shifts that risk to you, so it demands visible weekly reporting and a spending cap.
How the work is run beats the number of developers. Ask what happens when the scope changes, who writes the acceptance criteria and what the QA setup looks like. A team should be able to show you a working build every one or docker software development company two weeks. Acceptance criteria in writing are your only real protection against the it-was-never-in-scope conversation.
Finally, plan for the end of the engagement while the relationship is still good. Ask that the repository lives in your organisation from the first commit, and that a readme and architecture notes are kept current as the code changes. A provider confident in its own work will agree quickly; a long negotiation over it reveals quite a lot.
