How many environments should we have?

The number of environments is a trade-off between safety and maintenance.

Three is the norm

Development where things are tried out, testing where users verify them, and production where the work takes place. This provides a safe path from idea to operation without disrupting anyone.

Two is the absolute minimum

Production and one more. If you develop directly in production, users will encounter half-finished changes in the middle of the workday. Avoiding that isn't excessive caution — it's the bare minimum.

More is rarely better

Each environment requires storage and maintenance. Separate environments for each developer may be appropriate for large teams, but for most, they simply create more places to keep in sync.

The default environment doesn't count

All users have access to the default environment. It is not suitable for anything business-critical and should not be counted as one of the three.