Look first at domain experience, not the number of logos on the website. Ask for a couple of projects that sit close to your technology stack for web apps, and then find out which engineers actually built it. An honest provider is happy to connect you with the people who would work on your project. Evasive answers at this stage almost always mean the demo work came from somewhere else.

The contract needs more attention than the sales deck. Three sections matter more than the rest: assignment of intellectual property, confidentiality, and termination and handover. Everything produced must transfer to you once invoices are settled, including documentation, pipelines and deployment scripts. Watch for language that keeps reusable components outside the transfer, because that is often exactly the piece that locks you in.

Ask how they estimate. A credible estimate arrives with the assumptions behind it, a task-level breakdown and a range rather than a single number. A fixed price only makes sense when the scope is genuinely frozen; in any other case the vendor pads the number and you pay for it anyway. Hourly billing shifts that risk to you, so it needs a cap, regular demos and hire aiohttp developer transparent reporting.

Process beats headcount. Establish how a new requirement enters the plan, who defines done and how quality assurance works. A mature team will be able to walk you through a working build every one or two weeks. Acceptance criteria in writing remain the only reliable protection against endless rounds of rework.

Finally, think about the end of the engagement before it becomes urgent. Insist that the source repository lives under your account from the first commit, and that the documentation is refreshed in every sprint. A vendor with nothing to hide accepts it without argument; hesitation here tells you most of what you need to know.