Look first at proven experience, not the size of the portfolio. Ask to see a couple of projects that resemble your stack, and russia software development agency then ask specifically who actually wrote that code. A serious vendor is happy to connect you with the engineers. Evasive answers at this stage generally mean you are talking to a reseller.
The agreement needs more attention than the sales deck. Three sections matter more than the rest: assignment of intellectual property, the NDA, and hire vuejs developers termination and handover. Everything produced must transfer to you on payment, together with source code, designs and infrastructure as code. Be careful with wording that keeps framework code outside the transfer, as that is often the dependency that makes switching painful.
Ask where their numbers come from. A credible estimate comes with a list of assumptions, a breakdown per feature and an explicit range. A fixed-price contract works only when the specification is complete; when the scope is still moving the provider pads the number and you pay for uncertainty either way. Hourly billing puts the risk on your side, so it needs a sprint cadence, demos and a budget cap.
Process matters more than headcount. Find out what happens when the scope changes, who defines done and how quality assurance works. A well-run team should be able to show you a working build every one or two weeks. Written acceptance criteria remain the only reliable protection against endless rounds of rework.
Last, think about the day you no longer need this vendor while the relationship is still good. Require that the code repository stays under your account from the beginning, and that documentation is updated as part of the work. A partner who is comfortable with this will agree quickly; a long negotiation over it tells you a great deal.
