1. The Anatomy of Machine Coding Rounds
Popularized by companies like Uber, Swiggy, Flipkart, and Atlassian, the machine coding round requires candidates to design and implement a fully functioning, executable application in 90 to 120 minutes.
Interviewers evaluate: Working code (mandatory), Object-Oriented Modeling (interfaces, inheritance), Separation of Concerns (Controller, Service, Repository), Extensibility, and Unit Tests.
2. The 90-Minute Execution Plan
Minutes 0–15: Clarify requirements, list entities, and agree on assumptions with the interviewer.
Minutes 15–30: Define models and interfaces. Create enums, domain entities, and service contracts before writing any business logic.
Minutes 30–70: Implement the core service logic and strategy implementations.
Minutes 70–85: Write a simple driver `main()` method or automated unit tests demonstrating all requirements.
Minutes 85–90: Code cleanup, removing dead code, and walking the interviewer through your solution.
3. The Package Structure Formula
Always organize code into clean layers: `models/`, `enums/`, `strategies/`, `services/`, and `repository/`. This demonstrates modular architecture from the first minute.
Model this architecture on the HLDForge Canvas
Turn static box diagrams into living, collaborative systems. Drag and drop microservices, Kafka clusters, and cache tiers. Run automated SPOF detection and STRIDE threat modeling in real time.
Written by HLDForge Architecture Team
Lead Machine Coding Specialist
The HLDForge Architecture Team publishes practical engineering guides, real-world case studies, and high-concurrency blueprints to help engineers build scalable and fault-tolerant software.