How did you determine that it's time to change something? Based on which metrics?

The decision to make changes is usually based on metrics that reflect the quality and efficiency of the current solution. In the context of Golang and development in general, these can include:

• Performance: response time, throughput, CPU and memory usage. If the application starts to slow down or consumes too many resources, it’s worth considering refactoring or optimization.
• Reliability: number of errors, crashes, incidents. An increase in bugs or failures signals the need for improvements.
• Maintainability: code complexity, time to make changes, technical debt. If the code becomes difficult to maintain, it’s a reason for refactoring.
• Business logic metrics: for example, request processing time, user satisfaction.

Example: if API latency increases and exceeds SLA, or if the load increases and the application cannot cope, it’s time to change the architecture or optimize bottlenecks. Profiling (pprof), monitoring (Prometheus, Grafana), and logs can be used for measurement.