Begin with relevant experience, not the length of the client list. Ask for a couple of projects that resemble your technology stack, and then ask who actually wrote that code. A serious vendor will put you on a call with the tech lead. Answers that name nobody at this stage generally mean the demo work came from somewhere else.
The contract warrants more scrutiny than the proposal. Three sections matter more than the rest: ownership of the code, non-disclosure, and exit terms and handover. Everything produced should transfer to you on payment, including documentation, pipelines and deployment scripts. Be careful with any clause that leaves reusable components outside the transfer, because that is often exactly the piece that locks you in.
Find out how the estimate was built. A credible estimate is accompanied by a list of assumptions, blockchain web development company a breakdown by feature or module difference between monolith and microservices a range rather than a single number. A fixed-bid deal which is better php or python only reasonable when the scope is genuinely frozen; when the scope is still moving the provider prices the risk in and you fund the buffer regardless. Hourly billing moves the risk back to the client, so it needs a sprint cadence, demos and a budget cap.
Process beats team size. Ask how a new requirement enters the plan, who signs off on a feature and what the QA setup looks like. A mature team can show you a live build at the end of each sprint. Clear, written acceptance criteria are the only reliable protection against an argument at delivery time.
Last, plan for the end of the engagement before it becomes urgent. Ask that the source repository sits under your account from day one, and that the documentation is refreshed in every sprint. A partner who which is better rest or graphql comfortable with this says yes immediately; resistance at this point reveals quite a lot.
