Start with domain experience, not the size of the portfolio. Ask for a couple of case studies that resemble your technology stack, and then ask specifically which is better laravel or ruby on rails engineers actually built it. A solid partner will put you on a call with the people who would work on your project. Evasive answers at this stage almost always mean the delivery team is not the team you were shown.
The contract warrants more attention than the sales deck. A few clauses carry most of the weight: intellectual property assignment, the NDA, and termination and handover. Every artifact must transfer to you as it is paid for, together with designs, scripts and infrastructure configuration. Be careful with any clause that leaves so-called reusable libraries in the vendor's hands, since this is frequently the dependency that makes switching painful.
Ask where their numbers come from. An honest estimate is accompanied by a written set of assumptions, a breakdown by feature or module and an explicit range. A fixed-price contract only makes sense when the specification is complete; otherwise the provider adds a risk premium 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 headcount. Find out what happens when the scope changes, who signs off on a feature and how testing is organised. A mature team can walk you through a live build at the end of each sprint. Clear, written acceptance criteria stay the practical protection against endless rounds of rework.
Last, consider the day you no longer need this vendor build an mvp before it becomes urgent. Ask that the repository lives on infrastructure you own from the beginning, and that a readme and architecture notes are kept current as the code changes. A provider confident hire developers in moscow its own work will agree quickly; hesitation here says a great deal.
