A quote that comes back within a day counts as a bad sign. A competent team responds with questions first: about who owns the data and mobile development agency what happens on failure. A vendor that quotes without asking anything is simply pricing a guess, project based software development and a guess will be corrected later — on your budget.
Look out for any distance between the engineers on the sales call and those who eventually appear in the repository. Insist on named engineers in the contract, with a clause that requires notice before anyone is swapped. A provider that only offers roles and will not commit to specific engineers is keeping the right to assign anyone it likes.
Ask for the source repository from the first week. A team that shows code only at milestones expects you to take delivery on faith. Visible commits reveal who is really on the project far better than a slide deck. The same holds for the CI pipeline: if it does not exist, promises about quality are nothing more than words.
Vague contract language around code ownership is not an oversight. The agreement should state plainly that the code, designs and hire golang developers documentation transfer to your business as they are paid for. Check also the jurisdiction and how payments are structured: heavy prepayment with no milestone tied to it takes away any leverage you would otherwise keep.
Last, look at how they communicate. Establish how much working-time overlap you will share with your timezone, which person is expected to answer questions and within what time. Some genuine overlap is usually enough; no overlap stretches a five-minute question into a lost day. Careless writing in the early emails will not improve under delivery pressure.