Software development has its own stages often correlating to the available budget, particularly for startups. Small-medium-sized businesses and enterprises may not have such rigid constraints allowing them to ramp up and get their product to market faster.
Startups often start by bootstrapping their way to deliver a proof of concept or Minimum Viable Product to show investors. In these early stages, fully functional full-featured software isn’t required. You only need something for show – to illustrate the concept and prove your idea is viable. You can probably get by with a project manager, a few developers, and a designer – bypassing QA, BA, and DevOps. When you receive funding, you can scale up – as always keeping your funding runway in mind. Established businesses will still likely want to follow the MVP approach, but can ramp up the size of their team earlier if desired.
Most of the software development effort takes place before it is released to the public. Once released, it’s likely that you’ll need to keep most of the team in place to fix bugs. Thereafter, the development effort will diminish to just focus on improving performance. This is likely to continue for several years to keep your software commercially competitive. However, team requirements will taper off as it reaches the ends of its viable lifespan.