Look first at proven experience, not the length of the client list. Ask for a couple of case studies that match your domain and your stack, and then ask which engineers actually built it. An honest provider will put you on a call with the engineers. Answers that name nobody at this stage almost always mean the demo work came from somewhere else.
The contract needs more scrutiny than the proposal. A few clauses carry most of the weight: ownership of the code, confidentiality, and exit terms and handover. All the work product must transfer to you as it is paid for, including designs, scripts and infrastructure configuration. Watch for language that leaves reusable components with the vendor, aws web development company since that is often the part you cannot replace later.
Ask how they estimate. A serious estimate arrives with a written set of assumptions, a breakdown by feature or staff augmentation company module and an explicit range. A fixed price is only reasonable when the requirements are stable and documented; when the scope is still moving the supplier adds a risk premium and you pay for it anyway. Time and materials puts the risk on your side, so it requires a cap, regular demos and transparent reporting.
Process beats team size. Establish how change requests are handled, who defines done and how testing is organised. A team can walk you through a live build at the end of each sprint. Written acceptance criteria remain the practical protection against an argument at delivery time.
Finally, think about the day you no longer need this vendor while the relationship is still good. Require that the source repository lives under your account from the first commit, and kubernetes software development company that documentation is updated as part of the work. A provider confident in its own work accepts it without argument; resistance at this point reveals a great deal.