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System Design Architecture Playbook

A playbook for system design

PLAYBOOK #3: MASTERING SYSTEM DESIGN FOR HIGH-SCALE ARCHITECTURE

For: Senior Developers, Tech Leads & Software Architects

“A great system is not one that never fails. It is designed to fail gracefully.” This playbook helps you master high-scale system design thinking and overcome the toughest case study interviews.

PART 1: The Architect’s checklist

When designing, ask yourself: how will your system behave if traffic increases 100x within one second?

1. Scalability & Load Balancing

  • Vertical vs. Horizontal Scaling: When should you upgrade the server, and when should you add more nodes?
  • Load Balancing: Which algorithms fit each layer (Round Robin, Least Connections, Consistent Hashing)?
  • Caching Strategy: Optimize read-heavy systems with Redis or Memcached. Cache Aside, Write-through, or Write-back?

2. Database Design & Consistency (Data is the heart)

  • SQL vs. NoSQL: Analyze the trade-offs between consistency (ACID) and scalability.
  • Database Sharding & Replication: How to partition data to avoid bottlenecks. Understand Master-Slave vs. Multi-master.
  • CAP Theorem: Do you choose CP (Consistency & Partition Tolerance) or AP (Availability & Partition Tolerance)? Why?

3. Communication Patterns

  • Synchronous (REST, gRPC): When do you need immediate responses?
  • Asynchronous (Message Queues - Kafka, RabbitMQ): Use event-driven architecture to handle traffic spikes and decouple systems.

PART 2: Framework to Answer System Design Case Interviews

Do not draw the diagram immediately. Follow this four-step architect process:

  • Step 1: Understand Constraints: Ask about DAU/MAU, read/write ratio, and data retention.
  • Step 2: High-level Design: Sketch the main components (API Gateway, Load Balancer, Services, DB).
  • Step 3: Deep Dive: Zoom into sensitive points. Example: “How do we prevent double payments when the network lags?” (Idempotency).
  • Step 4: Identify Bottlenecks & Single Point of Failure (SPOF): Acknowledge weaknesses and propose fallback options.

PART 3: Reverse Interviewing: Read Engineering Culture

Ask these questions to understand whether you will join a team to build systems or to firefight every day.

  • Technical Debt: “Where is the biggest bottleneck today? What percentage of time goes into handling legacy code?”
  • Testing: “How are integration tests and load tests for high-traffic systems executed before go-live?”
  • Release: “Do you support canary releases or feature flags to reduce risk when making major architecture changes?”
  • Disaster Recovery: “If the primary database is completely down, how long is the recovery time objective (RTO) and what is the maximum data loss (RPO)?”

References for Architects

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