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System Design Architectures

Interactive technical blueprints, capacity estimates, database sharding strategies, and visual flowcharts for the top 30 system design interview questions.

Target Architectures
Infrastructure Component

Application Load Balancer (ALB)

High-performance Layer 7 routing mechanism distributing web traffic based on path rules, host headers, and SSL status.

1. System Requirements

Functional
  • Perform Layer 7 routing (HTTP paths, cookies, headers, query strings).
  • Handle TLS/SSL offloading (SSL termination) to offload cipher decryption from application servers.
  • Establish active health checks for targets to automatically redirect traffic away from failing servers.
Non-Functional / SLA
  • High availability across multiple Availability Zones.
  • Auto-scaling capacity to absorb unexpected traffic surges.
  • Support HTTP/2, WebSockets, and integration with WAF security systems.

2. Scale & Resource Estimates

Throughput: Dynamically scales from 1,000 to over 5,000,000 Requests Per Second (RPS) via DNS scaling.

Storage & RAM: Zero persistent storage. Tracks active TCP connections in dynamic routing tables (RAM footprint is ~10 KB per active socket).

3. System API Endpoints

// Route Request based on URL path
GET /api/v1/users  --> Target Group: user-service (Port 8080)
GET /api/v1/orders --> Target Group: order-service (Port 8081)

4. Database Schema Design

Memory tables mapping target nodes:
UserTargetGroup  = ["10.0.1.12:8080", "10.0.2.44:8080"]
OrderTargetGroup = ["10.0.1.15:8081", "10.0.2.98:8081"]

5. Interactive High-Level Architecture

graph TD Client[Client Browser] -->|HTTP/HTTPS Request| ALB[Application Load Balancer] ALB -->|Path: /users| UsersTG[Users Target Group] ALB -->|Path: /orders| OrdersTG[Orders Target Group] UsersTG --> ServerU1[User Instance A] UsersTG --> ServerU2[User Instance B] OrdersTG --> ServerO1[Order Instance A]

6. Scalability Deep Dive & Bottlenecks

ALBs operate at Layer 7 of the OSI model. When an HTTPS request arrives, the ALB terminates the SSL handshake, decrypts the request payload, inspects the headers (e.g. Host headers or Path cookies), and makes a routing decision using load balancing algorithms (Round Robin, Weighted, Least Outstanding Requests). Once a target is selected, it opens a fresh HTTP/1.1 or HTTP/2 connection to the backend node.

7. Production Scaling Strategies

DNS Round-Robin: AWS scales ALBs by expanding the list of IP addresses returned by the load balancer's domain name.

Connection Pooling: Keep-alive connections are maintained with target backends to avoid TCP handshake overhead on every client request.

Sticky Sessions: Route subsequent requests from the same user to the same target node using cookie attributes.

8. Runnable Production Starter Code

Scaffold