Begin with proven experience, not the number of logos on the php developer website. Request three or four case studies that sit close to your technology stack, and then ask whether those engineers are still with the company. An honest provider is happy to connect you with the engineers. Answers that name nobody at this stage generally mean the delivery team is not the team you were shown.
The contract warrants a slower read than the pitch. Three clauses do most of the work: intellectual property assignment, confidentiality, and termination and handover. Everything produced must transfer to you on payment, together with source code, designs and infrastructure as code. Be careful with language that leaves framework code outside the transfer, since this is frequently the dependency that makes switching painful.
Ask how they estimate. A serious estimate arrives with a written set of assumptions, custom kotlin development a breakdown per feature and an explicit range. A fixed-bid deal is only reasonable when the requirements are stable and documented; in any other case the vendor prices the risk in and you fund the buffer regardless. Time and materials shifts that risk to you, so it demands a sprint cadence, demos and a budget cap.
How the work is run beats team size. Establish how change requests are handled, who signs off on a feature and java outsourcing company what the QA setup looks like. A mature team should be able to demonstrate a live build at the end of each sprint. Written acceptance criteria stay the practical protection against the outsourcing it development-was-never-in-scope conversation.
Before signing, think about the end of the engagement while the relationship is still good. Ask that the source repository stays on infrastructure you own 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 most of what you need to know.