INTERVIEW ROUNDS

Low-level design and machine coding

You design and build a small working system in code: classes, interfaces, data structures and how they change when a new requirement arrives. In India, the 90-minute machine coding round (Flipkart, PhonePe, Swiggy, Razorpay) is often the first filter for SDE 2.

What happens

There are two flavours. In an object-oriented design round you talk through classes, relationships and design patterns for something like a parking lot, with some code. In a machine coding round you get a written spec and 60 to 120 minutes to build a working, runnable in-memory application, then defend it in a review where the interviewer adds a feature to see whether your design bends or breaks.

What is expected at each level

SDE 1 · New grad to about 2 years

Object-oriented design with clear classes and responsibilities. Working code matters more than patterns.

SDE 2 · About 2 to 5 years

The core round at many product companies: working, modular, extensible code with validation, error handling and tests, finished on time.

SDE 3 · Senior, about 5 to 10 years

Same as SDE 2 plus concurrency (two users booking the same seat) and a clean extension story.

SDE 4 · Staff, principal and above

Rare as a standalone round; folded into design discussions.

How to prepare

• Build five classic systems end to end under a 90-minute timer: parking lot, splitwise, snake and ladder, rate limiter, in-memory key-value store.
• Separate models, services and storage; keep the main method thin.
• Learn when to use strategy, factory and observer patterns, and when not to.
• Handle invalid input explicitly: graders check validation.

Common mistakes

• Code that does not run at the deadline
• One giant class
• Hard-coding a choice that the reviewer will ask to change
• Not matching the spec exactly: input format matters

Companies that use it

• Amazon · SDE 1, SDE 2
  Object-oriented design such as a parking lot or a coupon system is common for junior candidates and sometimes shows up in the Bar Raiser round.
• Apple · SDE 1, SDE 2
  Object-oriented or component design such as a contact search system or a memory-efficient image decoder, mostly for junior and mid-level roles.
• Uber · SDE 1, SDE 2, SDE 3
  Coding 2, 'Depth in Specialization', is often machine coding or object-oriented design for backend roles, such as file-system commands with concurrency.
• Atlassian · All levels
  The 'Code Design' half: build a small working component that can be extended, such as a popularity tracker, then handle new requirements, tie-breaks and concurrency.
• Goldman Sachs · All levels
  Class and schema design for a small system; concurrency follow-ups are frequent.
• Salesforce · SDE 2, SDE 3, SDE 4
  Object and concurrency design, such as a connection pool, often starting with database and sharding questions.
• Oracle · SDE 1, SDE 2, SDE 3
  Usually half a round: schema or class design.
• Adobe · SDE 2, SDE 3
  Schema design and modular code for a booking-style system, with queries against your schema.
• Flipkart · SDE 2, SDE 3
  Machine coding: about 90 minutes to build and submit a working app, then a 30-minute walkthrough of the code, sometimes the next day.
• Walmart Global Tech · SDE 2
  Some SE III loops include a medium LLD problem with Java concurrency follow-ups.
• PhonePe · SDE 1, SDE 2, SDE 3
  Machine coding: about 90 minutes to build a working in-memory app, then a 30-minute debrief full of 'why' questions.
• Swiggy · SDE 1, SDE 2, SDE 3
  Machine coding / LLD that expects compilable, modular code.
• Razorpay · SDE 1, SDE 2, SDE 3
  Machine coding: build a working in-memory system that matches the spec exactly, often the first round for lateral hires.

Other rounds

The online assessment (OA) · The phone screen · The coding round (DSA) · The AI-assisted coding round · The system design round (HLD) · Team-specific rounds · The behavioral round · The hiring manager round · The bar raiser round · Team match and hiring committee