Build a distributed Order Processing Pipeline

Last updated: January 28, 2026

Quick Overview

Design a distributed order processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Doordash
System Design
Software Engineer
Doordash
January 28, 2026
Software Engineer
Onsite
System Design
Easy

2

5

3,805 solved


Design a distributed order processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Doordash asks this during the Onsite to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.

What the Interviewer Expects
  • Clearly define functional and non-functional requirements
  • Propose a reasonable high-level architecture with core components
  • Choose appropriate data storage solutions with basic justification
  • Discuss basic scaling strategies (horizontal scaling, caching)
  • Identify potential bottlenecks and suggest simple solutions
Key Topics to Cover
Consistency models and replication
Failure handling and fault tolerance
Partitioning and sharding strategies
Requirements gathering and capacity estimation
Security and authentication
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 optimize costs as the system scales?
  • How would you migrate from a monolithic to a microservices architecture?
  • How would you handle schema migrations with zero downtime?
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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For distributed Order Processing Pipeline, key functional requirements in...

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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