Hiring in-house buys you long-term retention of knowledge. The engineers internalise the business domain over time, and that knowledge remains with you. The catch comes in the form of time difference between monolith and microservices rigidity: hiring well takes months, ramping up adds more time, and the payroll carries on whether the roadmap is full or empty.
Handing a project to a vendor implies an external team owns the outcome: the partner staffs the project, the partner manages the plan, and they carry the delivery risk. This fits well when the outcome can be described and you have an available product owner. It works badly when there is no one to answer questions, because an external team will not fill that gap for you.
Hiring individual contractors falls in the middle: you rent capacity while keeping the planning and the management on your side. It is fast — a matching profile can join almost immediately — and it winds down as quickly as it ramped up. The trade-off is that your technical leaders need time for code review and planning. Without that, you end up paying hourly for uncoordinated work.
Most of the time, these models are combined. A common pattern keeps the architecture and the core domain with permanent staff, kotlin development agency while an outside vendor takes on the parts that are bounded and specifiable. The rule is easy to state: retain what defines your product, and delegate the well-trodden work.
A few questions resolve most of these debates. To begin with: is what you are building central to how you make money, or a supporting tool? Second: web server performance comparison over what horizon will the work last — one project or a permanent roadmap? Last: who will maintain it in two years? Work through them with real answers and the appropriate option is normally clear.