Firewall & WAF
Web Application Firewall filtering Layer 7 exploits (SQLi, XSS) and defending perimeter network layers from malicious traffic.
1. System Requirements
- Inspect incoming request bodies, headers, and cookies for malicious payloads (XSS, SQL Injection).
- Block suspicious IP addresses, botnet user-agents, and geographic locations.
- Inject rate limits per client IP or request fingerprint.
- Minimal routing latency overhead (< 3ms rule checking).
- Fault tolerance: WAF failures should default to closed/secure or open depending on security profiles.
2. Scale & Resource Estimates
Throughput: Performs full inspection on gigabits of raw traffic per second, scaling horizontally across edge endpoints.
Storage & RAM: Stores security rule indices, temporary IP blacklist counters, and telemetry audit logs.
3. System API Endpoints
// Evaluate Request Rule
If (Request.Body contains "UNION SELECT") -> HTTP 403 Forbidden
If (Request.Headers["User-Agent"] in bot_list) -> HTTP 403 Forbidden4. Database Schema Design
Blacklist Schema (Redis Cache):
Blocked_IP_Set = { "198.51.100.12", "203.0.113.88" } (TTL: 3600)5. Interactive High-Level Architecture
6. Scalability Deep Dive & Bottlenecks
WAFs protect application layers by executing rule inspection engines. These engines compile regular expressions or signature files mapping SQL injection, cross-site scripting (XSS), file inclusion, and HTTP floods. Modern cloud firewalls (like AWS WAF or Cloudflare) execute checks at edge endpoints closer to the user to block malicious traffic before it reaches the backend network layers.
7. Production Scaling Strategies
Edge Deployment: Running rule checks on global Edge networks (CDNs) to offload work from target data centers.
Rate Limiting Rules: Aggregating request counters by IP keys in fast distributed memory arrays to reject Layer 7 floods.
Rule Compilations: Optimizing regexp execution engines to inspect payloads in constant O(1) time.
8. Runnable Production Starter Code
Scaffold