Traditional web cache proxy servers operate by intercepting and storing frequently accessed HTTP resources. However, HTTPS (HTTP over TLS) fundamentally changes this dynamic through end-to-end encryption. When examining packet flows:

// Traditional HTTP caching flow
Client → Proxy → Internet
    (Proxy can read/modify/cache content)

// HTTPS flow with TLS 1.3
Client → Internet
    (Proxy sees only encrypted handshake and data)

Modern TLS implementations present three primary obstacles:

• Perfect Forward Secrecy: Ephemeral keys prevent decryption of stored traffic
• SNI Encryption: ESNI/ECH hides requested hostnames
• Certificate Pinning (HPKP): Prevents MITM approaches

Several enterprise solutions have emerged:

// Example: Explicit proxy configuration with MITM
const agent = new https.Agent({
  rejectUnauthorized: false, // For testing only
  ca: [fs.readFileSync('proxy_cert.pem')]
});

Cloudflare's Cacheable HTTPS Content initiative demonstrates one approach using:

1. Cache-Control headers with public directive
2. Strict expiration policies
3. Edge-side includes for dynamic content

Comparative tests show:

The IETF is working on multiple fronts:

• QUIC's built-in caching mechanisms
• Oblivious HTTP for privacy-preserving caching
• Distributed Cache Protocols using homomorphic encryption

// Example QUIC server push for cache priming
const quic = require('net').createQUICSocket();
quic.onStream = (stream) => {
  stream.pushStream({
    ':path': '/static/logo.png',
    'cache-control': 'public, max-age=3600'
  });
};

For organizations requiring both security and caching:

1. Implement transparent TLS termination at edge
2. Use split-tier caching with clear-text internal storage
3. Adopt content-defined chunking for partial updates

Modern web infrastructure faces a fundamental tension between encryption and caching efficiency. With Let's Encrypt making TLS certificates free and automated since 2015, HTTPS adoption has skyrocketed from ~40% to over 90% of web traffic today. This creates significant challenges for traditional caching mechanisms.

Traditional proxy caches like Squid operate through:

# Standard HTTP cache workflow
1. Client → Proxy: GET /resource
2. Proxy checks local cache
3a. If cached: Proxy → Client: 200 OK (cached)
3b. Else: Proxy → Origin: GET /resource

HTTPS breaks this model because:

• End-to-end encryption prevents proxy inspection of URLs/headers
• Certificate validation requires direct client-server connection
• TLS session resumption tickets bypass proxy caching layers

Several approaches have emerged to maintain caching benefits while preserving security:

1. Explicit Proxy Configuration:

// Browser proxy auto-config (PAC) example
function FindProxyForURL(url, host) {
    if (shExpMatch(url, "*.example.com/*")) {
        return "PROXY cache.internal:8080; DIRECT";
    }
    return "DIRECT";
}

2. TLS Termination at Edge:
CDNs like Cloudflare implement split-tier TLS:

Client → CDN: HTTPS (TLS 1.3)
CDN → Origin: Optional HTTPS
CDN cache serves static content with:
  Cache-Control: public, max-age=86400
  Age: 4235 (seconds since origin fetch)

3. Keyless SSL Architectures:
Allows caching while keeping private keys secure:

// Simplified keyless SSL flow
1. Proxy receives ClientHello
2. Forwards signature request to key server
3. Completes handshake after receiving signed ServerKeyExchange
4. Caches encrypted content without key access

Studies show HTTPS adds ~30-100ms latency per request. Effective caching can reduce this:

Emerging standards address these challenges:

• HTTP/3 with QUIC: Built-in encryption with improved cache hints
• Encrypted Cache Keys: RFC 8246 allows secure content addressing
• Privacy-Preserving Prefetch: Differential privacy for cache prediction

The key insight: While traditional transparent caching becomes difficult with HTTPS, strategic architectural choices can preserve most performance benefits without compromising security.