Begin with domain experience, not the size of the portfolio. Ask for three or four engagements that resemble your stack, and then ask specifically which engineers actually built it. A serious vendor will introduce you to the tech lead. Answers that name nobody at this stage generally mean you are talking to a reseller.

The contract warrants a slower read than the pitch. Three sections matter more than the rest: intellectual property assignment, confidentiality, and exit terms and handover. Everything produced has to transfer to you as it is paid for, minimum viable product development company including documentation, pipelines and deployment scripts. Look closely at language that leaves framework code with the vendor, as this is frequently the dependency that makes switching painful.

Ask where their numbers come from. A serious estimate arrives with a list of assumptions, a breakdown by feature or hire expert node js developers module and a best case and a worst case. A fixed price works only when the scope is genuinely frozen; otherwise the provider prices the risk in and you pay for uncertainty either way. Hourly billing puts the risk on your side, so it requires a sprint cadence, demos and a budget cap.

The delivery process matters as much as headcount. Establish how change requests are handled, who signs off on a feature and what the QA setup looks like. A mature team will be able to show you a live build at the end of each sprint. Clear, written acceptance criteria are the only reliable protection against endless rounds of rework.

Last, consider the day you no longer need this vendor before it becomes urgent. Ask that the repository lives under your account from the beginning, and that a readme and architecture notes are kept current as the code changes. A provider confident in its own work says yes immediately; a long negotiation over it tells you a great deal.