Build a event-driven Logging Pipeline

Last updated: April 1, 2026

Quick Overview

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

Datadog
System Design
Software Engineer
Datadog
April 1, 2026
Software Engineer
System Design Round
System Design
Medium

26

8

1,976 solved


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

This is a common system design question asked during System Design Round at Datadog. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Datadog values engineers who can think about scalability from day one.

What the Interviewer Expects
  • Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
  • Design a scalable architecture with clear component responsibilities
  • Make well-reasoned database and caching decisions with trade-off analysis
  • Address consistency vs availability trade-offs specific to the use case
  • Discuss partitioning strategy, replication, and data modeling
  • Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
API design and rate limiting
Monitoring, logging, and alerting
Partitioning and sharding strategies
Failure handling and fault tolerance
Requirements gathering and capacity estimation
Caching strategies (local, distributed, CDN)
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 handle a region-wide outage?
  • How do you ensure data consistency across multiple services?
  • How would you optimize costs as the system scales?
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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For event-driven Logging Pipeline, key functional requirements include: w...

Capacity Estimation

Estimate the scale to drive design decisions. Assume 100M DAU with an average of 10 actions per user per day = 1B requests/day ~ 12K QPS average, ~36K...


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