Look first at domain experience, not the size of the portfolio. Ask to see two or three projects that match your technology stack, and then ask specifically who actually wrote that code. A serious vendor custom web development services is happy to connect you with the engineers. Answers that name nobody at this stage usually mean you are talking to a reseller.
The agreement deserves more scrutiny than the proposal. Three sections matter more than the rest: ownership of the code, the NDA, and exit terms and handover. Everything produced has to transfer to you on payment, along with source code, designs and infrastructure as code. Be careful with any clause that leaves so-called reusable libraries in the vendor's hands, because this is frequently the part you cannot replace later.
Find out how the estimate was built. An honest estimate comes with a list of assumptions, a breakdown per feature and symfony vs laravel performance a best case and a worst case. A fixed-price contract only makes sense when the scope is genuinely frozen; when the scope is still moving the vendor prices the risk in and you fund the buffer regardless. A time-and-materials model moves the risk back to the client, so it needs visible weekly reporting and a spending cap.
Process matters more than team size. Find out how a new requirement enters the plan, who signs off on a feature and edtech software development services how testing is organised. A team can demonstrate running igaming software rather than status reports. Clear, written acceptance criteria stay the only reliable protection against an argument at delivery time.
Finally, consider the handover at the start rather than at the end. Insist that the source repository lives under your account from the first commit, and that documentation is written as you go rather than left to the end. A vendor with nothing to hide accepts it without argument; a long negotiation over it reveals a great deal.
