System Design Interview Preparation

System design interviews assess your ability to design scalable, reliable systems. This guide covers core concepts and real-world scenarios for .NET developers.

Core Concepts

Scalability

• Horizontal vs Vertical Scaling
• Load Balancing
• Caching Strategies

Reliability

• Fault Tolerance
• Redundancy
• Health Checks

Performance

• Latency Optimization
• Throughput Maximization
• Database Indexing

Common Patterns

Caching

When to use: Frequently accessed, rarely changing data

public async Task<Product> GetProductAsync(int id)
{
    var cacheKey = $"product:{id}";
    var cached = await _cache.GetStringAsync(cacheKey);
    
    if (cached != null)
        return JsonSerializer.Deserialize<Product>(cached);
    
    var product = await _db.Products.FindAsync(id);
    await _cache.SetStringAsync(cacheKey, JsonSerializer.Serialize(product));
    
    return product;
}

Message Queues

When to use: Async processing, decoupling services

Load Balancing

Types: Round Robin, Least Connections, IP Hash

Interview Framework

1. Clarify Requirements (5 min)
2. High-Level Design (10 min)
3. Deep Dive (15 min)
4. Bottlenecks & Trade-offs (5 min)
5. Scaling Strategy (5 min)

Related Topics

• Microservices
• Azure Architecture