Module 8 - Networking and APIs

Compression Techniques

Shrink data to save bandwidth and speed up transfers.

1The Vacuum Bag Analogy

Simple Analogy
Vacuum bags compress bulky clothes by removing air. You can fit 3x more in your suitcase. Compression works similarly-it removes redundancy from data so you can transmit 3-10x less over the network.

Compression reduces data size by encoding information more efficiently. Trade CPU cycles for bandwidth savings.

2Common Algorithms

gzip

60-80% smallerMedium

Industry standard. Widely supported. Good balance of speed and ratio.

Best for: HTTP responses, file archiving

Brotli

70-85% smallerSlow (compress), Fast (decompress)

Better compression than gzip. Modern browsers support it.

Best for: Static assets, CDN, pre-compressed files

LZ4

50-60% smallerVery Fast

Optimized for speed over ratio. Great for real-time.

Best for: Database storage, Kafka, real-time streaming

Zstandard (zstd)

65-85% smallerFast

Facebook's algorithm. Configurable speed/ratio tradeoff.

Best for: Logs, backups, modern systems

3HTTP Compression

Request/Response Headers
// Client advertises what it can decompress
Accept-Encoding: gzip, deflate, br

// Server responds with what it used
Content-Encoding: gzip

// Browser automatically decompresses
// No extra client code needed!
Compress These
  • ✓JSON responses
  • ✓HTML, CSS, JS
  • ✓Text-based formats
  • ✓SVG images
Skip These
  • ⚠JPEG, PNG, WebP (already compressed)
  • ⚠Video/audio files
  • ⚠Encrypted data
  • ⚠Very small responses (<1KB)

4Real Impact

ContentOriginalgzipBrotli
JSON API response100 KB25 KB (75%)20 KB (80%)
React bundle500 KB150 KB (70%)120 KB (76%)
HTML page50 KB12 KB (76%)9 KB (82%)
JPEG image200 KB198 KB (1%)197 KB (1.5%)

5When to Compress

API responses (JSON)

Always. gzip is standard. 70-80% reduction.

Static assets (JS, CSS)

Pre-compress with Brotli. Serve from CDN.

Real-time data (streaming)

LZ4 or skip. CPU matters more than size.

Database storage

LZ4 for hot data, zstd for cold. Balance speed/space.

Very small payloads (<1KB)

Skip. Overhead may exceed savings.

6Server Configuration

Nginx
gzip on;
gzip_types application/json 
           text/css 
           application/javascript;
gzip_min_length 1000;

# Brotli (module required)
brotli on;
brotli_types application/json;
Express.js
const compression = require('compression');

app.use(compression({
  threshold: 1024, // min 1KB
  level: 6, // 1-9, higher = smaller but slower
  filter: (req, res) => {
    // Don't compress images
    if (req.path.match(/\.(jpg|png)$/)) {
      return false;
    }
    return true;
  }
}));

7Key Takeaways

1gzip is the standard for HTTP. 70-80% reduction on text.
2Brotli is better but slower. Great for static assets.
3LZ4 for speed-critical: real-time, databases, Kafka.
4Don't compress already-compressed files (JPEG, PNG, video).
5Set minimum size threshold (~1KB). Small files not worth it.

?Quiz

1. API returns 50KB JSON. Should you compress?

2. Best compression for real-time streaming?