How have you optimized queries in practice? What do you look at when a query slows down?

When optimizing queries in Go, I usually start with analyzing bottlenecks:

• Profiling: I use pprof for CPU and memory to understand where time and resources are spent.
• Logging and metrics: I look at execution time, call frequency, errors.
• Handler code analysis: I check for redundant operations, repeated database queries, heavy computations.
• Database optimization: I examine the number and complexity of SQL queries, indexes, caching.
• Parallelism and asynchrony: If possible, I parallelize requests or make them asynchronous.

For example, if a handler is slow due to long database queries, caching can be added, prepared statements can be used, or SQL can be optimized. If serialization is the issue, faster formats can be used or the amount of data transmitted can be reduced.

Profiling CPU code:

import (
    "net/http"
    _ "net/http/pprof"
)

func main() {
    go func() {
        log.Println(http.ListenAndServe("localhost:6060", nil))
    }()
    // main logic
}

This allows connecting to the profiler and understanding where bottlenecks are.