Look first at relevant experience, not the length of the client list. Ask to see three or four engagements that match your stack, and then ask specifically who actually wrote that code. A serious vendor vue js vs angular will introduce you to the people who would work on your project. Vague answers at this stage generally mean the delivery team is not the team you were shown.
The contract warrants more attention than the sales deck. Three sections matter more than the rest: ownership of the code, confidentiality, and exit terms and handover. Everything produced has to transfer to you on payment, together with source code, fintech software development company designs and infrastructure as code. Be careful with any clause that keeps so-called reusable libraries outside the transfer, because it is usually exactly the piece that locks you in.
Ask how they estimate. A credible estimate is accompanied by the assumptions behind it, a breakdown per feature and a range rather than a single number. A fixed-price contract only makes sense when the requirements are stable and documented; when the scope is still moving the vendor adds a risk premium and symfony development outsourcing you pay for uncertainty either way. Time and materials moves the risk back to the client, so it requires a cap, regular demos and transparent reporting.
How the work is run matters as much as team size. Ask what happens when the scope changes, who defines done and laravel development agency how testing is organised. A mature team can demonstrate a live build at the end of each sprint. Written acceptance criteria remain the only reliable protection against endless rounds of rework.
Finally, plan for the handover while the relationship is still good. Ask that the source repository sits in your organisation from day one, and that the documentation is refreshed in every sprint. A vendor with nothing to hide says yes immediately; resistance at this point tells you most of what you need to know.
