Build a scalable Logging Pipeline

Last updated: May 21, 2026

Quick Overview

Design a scalable logging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

HRT
System Design
Software Engineer
HRT
May 21, 2026
Software Engineer
Technical Screen
System Design
Hard

55

12

2,250 solved


Design a scalable logging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

System design interviews at HRT typically last 45-60 minutes. You are expected to drive the conversation, starting from requirements gathering through to a detailed architecture. The interviewer will evaluate your ability to handle ambiguity and make practical engineering decisions.

What the Interviewer Expects
  • Drive the design discussion proactively with minimal interviewer guidance
  • Perform detailed capacity estimation and use it to inform design decisions
  • Design for global scale with multi-region deployment and data consistency
  • Deep dive into 2-3 critical components with implementation-level detail
  • Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
  • Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
  • Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
Database selection and data modeling
Message queues and async processing
Load balancing and horizontal scaling
Consistency models and replication
How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
  • How would you migrate from a monolithic to a microservices architecture?
  • How would you optimize costs as the system scales?
  • How would you handle a 10x increase in traffic overnight?
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Sample Answer
Requirements

Functional Requirements

  1. Log Ingestion: The system should accept logs from various sources (web servers, microservices, etc.) in real-time.
  2. Log Storage: Logs should be stored in a sea...
Capacity Estimation

Back-of-Envelope Calculations

  1. Log Generation Rate: Assume 10 million logs per minute from various services.
  2. Size of Log Entry: Average size of a log entry is 1 KB.
  3. **Total Logs pe...

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