How to Optimize JSON Encoding/Decoding in Go

Optimize JSON encoding and decoding in Go by reusing buffers and pre-allocating slices to minimize memory allocations. Use json.Decoder with a bytes.Buffer for streaming large payloads, or pre-allocate []byte slices for known sizes before calling json.Marshal or json.Unmarshal.

import (
	"bytes"
	"encoding/json"
)

// Pre-allocate buffer for known sizes to reduce allocations
var buf bytes.Buffer

// Reuse buffer for multiple marshals
buf.Reset()
err := json.Compact(&buf, data)

// Use Decoder for streaming large JSON
decoder := json.NewDecoder(reader)
for decoder.More() {
	var item MyStruct
	decoder.Decode(&item)
}

JSON processing in Go often slows down because the program constantly creates and destroys memory blocks for every character it reads or writes. By reusing a single memory block (buffer) for these operations, you avoid the overhead of constantly asking the system for new memory. Think of it like using a reusable shipping box instead of buying a new one for every item you send.