Begin with relevant experience, not the number of logos on the website. Ask to see two or three engagements that match your domain and your stack, and then ask specifically who actually wrote that code. A solid partner is happy to connect you with the engineers. Answers that name nobody at this stage almost always mean the delivery team is not the team you were shown.

The paperwork deserves more scrutiny than the proposal. A few clauses carry most of the weight: ownership of the code, non-disclosure, and exit terms and handover. All the work product must transfer to you once invoices are settled, blockchain consulting services along with source code, designs and infrastructure as code. Look closely at language that leaves so-called reusable libraries with the vendor, as it is usually exactly the piece that locks you in.

Ask where their numbers come from. An honest estimate arrives with a list of assumptions, a task-level breakdown and a range rather than a single number. A fixed price is only reasonable when the specification is complete; in any other case the provider pads the number and you pay for uncertainty either way. Hourly billing puts the risk on your side, so it needs visible weekly reporting and a spending cap.

The delivery process beats headcount. Find out how a new requirement enters the plan, who signs off on a feature and how quality assurance works. A well-run team will be able to show you running software rather than status reports. Written acceptance criteria remain the only reliable protection against the it-was-never-in-scope conversation.

Before signing, consider the end of the engagement at the start rather than at the end. Require that the repository sits in your organisation from the beginning, and that the documentation is refreshed in every sprint. A vendor react development company with nothing to hide says yes immediately; resistance at this point says a great deal.