Begin with domain experience, not the length of the client list. Ask for a couple of engagements that sit close to your technology stack, and then ask which engineers actually built it. A serious vendor is happy to connect you with the tech lead. Vague answers at this stage almost always mean the delivery team is not the team you were shown.
The contract deserves more attention than the sales deck. Three sections matter more than the rest: ownership of the code, confidentiality, and termination and handover. Every artifact has to transfer to you once invoices are settled, next js vs laravel performance along with designs, swift development agency scripts and infrastructure configuration. Watch for any clause that leaves so-called reusable libraries in the vendor’s hands, because this is frequently the dependency that makes switching painful.
Find out how the estimate was built. A credible estimate comes with the assumptions behind it, a breakdown per feature and a range rather than a single number. A fixed price is only reasonable when the requirements are stable and documented; in any other case the provider adds a risk premium and you fund the buffer regardless. A time-and-materials model moves the risk back to the client, so it needs a cap, regular demos and transparent reporting.
The delivery process matters more than headcount. Establish what happens when the scope changes, who writes the acceptance criteria and angular development outsourcing how quality assurance works. A well-run team should be able to demonstrate a live build at the end of each sprint. Clear, written acceptance criteria stay the only reliable protection against endless rounds of rework.
Finally, plan for the day you no longer need this vendor before it becomes urgent. Ask that the source repository lives in your organisation from day one, and that the documentation is refreshed in every sprint. A provider confident in its own work says yes immediately; hesitation here tells you most of what you need to know.