When your process deserves its own software
Custom development is useful when an important business workflow cannot be supported well through existing products or reasonable configuration. It gives you control over the experience and integration model, along with responsibility for maintaining the result.
Evaluate fit before building
Compare the requirements against available software. Distinguish business-critical differences from preferences that can change. Building makes more sense when the process is stable enough to describe and valuable enough to justify ongoing engineering.
Design for the whole lifecycle
The first release is only part of the cost. Include deployment, monitoring, security updates, backups, documentation, and support in the plan. Agree on source-code access and ownership of infrastructure accounts. A maintainable system should be understandable to the team that operates it.
Deliver evidence early
Use working increments to test assumptions with real users. Review the main workflows before expanding scope. Clear acceptance criteria, demonstrations, and recorded decisions help keep the project aligned with its business purpose.