Begin with proven experience, not the length of the client list. Ask for a couple of case studies that sit close to your stack, and then ask who actually wrote that code. A serious vendor will put you on a call with the tech lead. Vague answers at this stage almost always 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: assignment of intellectual property, non-disclosure, and symfony development services notice periods and handover. All the work product should transfer to you on payment, including source code, designs and infrastructure as code. Watch for top react development companies language that leaves so-called reusable libraries in the vendor’s hands, since that is often exactly the piece that locks you in.
Ask how they estimate. An honest estimate is accompanied by a list of assumptions, a breakdown by feature or module and a range rather than a single number. A fixed-price contract only makes sense when the scope is genuinely frozen; otherwise the vendor prices the risk in and you pay for uncertainty either way. Hourly billing puts the risk on your side, so it requires visible weekly reporting and a spending cap.
Process matters more than team size. Establish what happens when the scope changes, who writes the acceptance criteria and how quality assurance works. A well-run team will be able to walk you through a live build at the end of each sprint. Acceptance criteria in writing are your only real protection against an argument at delivery time.
Before signing, think about the handover before it outsourcing dubai becomes urgent. Ask that the code repository lives on infrastructure you own from the beginning, and that documentation is updated as part of the work. A vendor with nothing to hide will agree quickly; hesitation here tells you quite a lot.