## Memory and Performance

### Preallocate Slices When Size is Known

```go
// Bad: Grows slice multiple times
func processItems(items []Item) []Result {
    var results []Result
    for _, item := range items {
        results = append(results, process(item))
    }
    return results
}

// Good: Single allocation
func processItems(items []Item) []Result {
    results := make([]Result, 0, len(items))
    for _, item := range items {
        results = append(results, process(item))
    }
    return results
}
```

### Use sync.Pool for Frequent Allocations

```go
var bufferPool = sync.Pool{
    New: func() interface{} {
        return new(bytes.Buffer)
    },
}

func ProcessRequest(data []byte) []byte {
    buf := bufferPool.Get().(*bytes.Buffer)
    defer func() {
        buf.Reset()
        bufferPool.Put(buf)
    }()

    buf.Write(data)
    // Process...
    return buf.Bytes()
}
```

### Avoid String Concatenation in Loops

```go
// Bad: Creates many string allocations
func join(parts []string) string {
    var result string
    for _, p := range parts {
        result += p + ","
    }
    return result
}

// Good: Single allocation with strings.Builder
func join(parts []string) string {
    var sb strings.Builder
    for i, p := range parts {
        if i > 0 {
            sb.WriteString(",")
        }
        sb.WriteString(p)
    }
    return sb.String()
}

// Best: Use standard library
func join(parts []string) string {
    return strings.Join(parts, ",")
}
```