How to find a slow query? Have you had experience optimizing such queries?

To find slow queries in a Go application, several approaches are usually used:

1. Logging query execution times. For example, wrapping calls with a timer and logging the duration.
2. Profiling with pprof — allows you to see where the application spends most of its time.
3. Using specialized monitoring tools (Prometheus, Jaeger, Zipkin) for tracing requests.

Optimizing slow queries may include:

• Analyzing SQL queries with EXPLAIN, adding indexes.
• Caching results.
• Rewriting logic to reduce the number of queries.

An example of simple query time logging:

start := time.Now()
// call function or query
result, err := db.QueryContext(ctx, "SELECT ...")
duration := time.Since(start)
log.Printf("Query took %s", duration)

This approach helps identify problematic areas and take measures for optimization.