6.1Cache Placement and Eviction Policies

Explanation
Caching improves system performance by storing frequently accessed data in faster storage layers closer to the client or application. Instead of repeatedly fetching data from a database or external service, the system serves responses from cache, reducing latency and load on core components. In system design, deciding where to place caches is as important as deciding what to cache.

Caches can exist at multiple levels, including browser caches, CDNs, application-level caches, and database caches. Eviction policies determine which data is removed when the cache is full. In 2026, effective caching strategies are designed with data freshness, consistency, and invalidation mechanisms in mind, as stale data can cause serious correctness issues.

Example
A news website caches article content at the CDN level so users around the world receive pages quickly. The application layer caches popular articles to reduce database queries, while personalized content bypasses the cache to ensure accuracy. When an article is updated, cache invalidation is triggered to maintain consistency across layers. This layered approach balances performance with correctness.

Use Cases

• High-read applications  
• Reducing database load  
• Improving global response times  
• Supporting traffic spikes

6.2 Performance Bottlenecks

Identifying and Fixing Hotspots

Explanation
Performance bottlenecks occur when a specific component limits overall system throughput or increases latency. Common bottlenecks include slow database queries, synchronous dependencies, network latency, and resource contention. Effective system design involves proactively identifying these hotspots and designing the system to minimize their impact.

In 2026, performance optimization is tightly coupled with observability. Metrics, logs, and traces are used to pinpoint where time and resources are being consumed. System designers must also consider the law of diminishing returns, focusing optimization efforts where they deliver the most value rather than prematurely optimizing every component.

Example
An analytics dashboard experiences slow page loads during peak usage. Monitoring reveals that a single database query dominates response time. By adding appropriate indexes and caching aggregated results, response times improve significantly. This targeted optimization demonstrates how identifying the right bottleneck leads to meaningful performance gains.

Use Cases

• Optimizing user experience  
• Reducing infrastructure costs  
• Supporting real-time systems  
• Improving system reliability

Conclusion

System design is a foundational skill that shapes how software is built, scaled, and maintained over time. As systems grow in complexity and reach, the ability to design thoughtfully becomes more important than the ability to write isolated pieces of code. In 2026, engineers are expected to think beyond features and consider reliability, scalability, cost, and long-term maintainability from the very beginning.

This guide is intended to help build that way of thinking. By focusing on fundamentals first and layering complexity gradually, it encourages deep understanding rather than pattern memorization. The principles covered here remain relevant regardless of specific technologies, making them valuable across different domains and career stages.

Mastering system design enables engineers to make informed architectural decisions, communicate ideas clearly, and build systems that can adapt to change. It is a skill developed through continuous learning and practice, and this guide serves as a structured foundation for that journey.

Additional Readings

Designing Data-Intensive Applications by Martin Kleppmann
System Design Primer (open-source repository)
Google Site Reliability Engineering Handbook
High Scalability architecture case studies
Cloud provider architecture and best-practice documentation
Distributed systems academic lecture notes
Engineering blogs from large-scale technology companies

Links for AlmaBetter Reference:

For learning System Design in 2026, AlmaBetter provides a comprehensive ecosystem through their "Bytes" platform. Although they may not have one single article with that exact title, they have a cluster of specialized roadmaps and deep dives that form a complete curriculum.

???? AlmaBetter System Design Resources