Look first at proven experience, not the size of the portfolio. Ask to see two or three case studies that match your stack, and symfony vs spring 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. Vague answers at this stage usually mean the demo work came from somewhere else.

The paperwork needs more attention than the sales deck. A few clauses carry most of the weight: ownership of the code, confidentiality, and exit terms and handover. Every artifact should transfer to you on payment, together with designs, typescript web development services scripts and infrastructure configuration. Be careful with wording that keeps framework code outside the transfer, since this is frequently the dependency that makes switching painful.

Ask how they estimate. An honest estimate is accompanied by a list of assumptions, a breakdown per feature and an explicit range. A fixed-price contract works only when the requirements are stable time and materials vs fixed price documented; in any other case the supplier 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.

How the work is run beats the number of developers. Establish how change requests are handled, who writes the acceptance criteria and how quality assurance works. A mature team can walk you through a working build every one or two weeks. Clear, written acceptance criteria stay the only reliable protection against endless rounds of rework.

Before signing, think about the end of the engagement before it becomes urgent. Require that the code repository sits on infrastructure you own from day one, and that documentation is updated as part of the work. A provider confident in its own work says yes immediately; a long negotiation over it tells you most of what you need to know.