Design Order Processing Infrastructure for microservices

Last updated: December 26, 2025

Quick Overview

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

Morgan Stanley
Software Engineering Fundamentals
Software Engineer
Morgan Stanley
December 26, 2025
Software Engineer
Technical Screen
Software Engineering Fundamentals
Medium

85

3

4,227 solved


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

Morgan Stanley asks this during the Technical Screen to assess your depth in software engineering. They want to see understanding of design patterns, system architecture, and the trade-offs involved in different technical approaches.

What the Interviewer Expects
  • Apply engineering principles to a realistic design scenario
  • Discuss trade-offs between different approaches with concrete examples
  • Demonstrate understanding of testability, maintainability, and extensibility
  • Connect theoretical concepts to production engineering practices
  • Discuss how the approach scales with team and codebase size
Key Topics to Cover
API design and RESTful conventions
Design patterns (Factory, Observer, Strategy, etc.)
SOLID principles
Testing strategies (unit, integration, e2e)
How to Approach This
  1. Apply SOLID principles. Single Responsibility makes code testable, Open/Closed makes it extensible.
  2. Choose data structures based on access patterns, not familiarity.
  3. Prefer immutable data and message passing over shared mutable state for concurrency.
  4. Design APIs with RESTful conventions, versioning, meaningful errors, and pagination from day one.
Possible Follow-up Questions
  • How would you document this for other engineers?
  • What testing strategy would you use for this component?
  • How would this design change if the team size doubled?
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Sample Answer
Core Principles

Start by identifying which engineering principles are most relevant: **SOLID Principles**: Single Responsibility (one reason to change), Open/Closed ...

Design Approach

**API Design**: Define clear interfaces before implementation. Use RESTful conventions for HTTP APIs. Version your APIs from the start. Return meaning...


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