Mckinsey Software engineering case interview

McKinsey SWE case interviews are problem solving interviews focused on system design, algorithms, and structured thinking, with a light business wrapper.

What you can expect

• Backend system design or data flow problems
• API design and service decomposition
• Basic algorithmic thinking (not LeetCode hard)
• Trade offs around scalability, latency, reliability
• Occasionally a simple estimation or prioritization question

Examples:

• Design a service to ingest and process large volumes of events
• Architect a recommendation or matching system at high level
• Debug or improve a poorly performing system
• Decide how to scale an internal tool globally

How deep they go

• High level architecture first, then drill into one or two components
• You are not expected to code full solutions
• Clear assumptions and trade offs matter more than syntax

How to prep in 3 days

• Review system design basics (APIs, databases, queues, caching)
• Practice explaining architectures clearly and simply
• Do a few mock problems out loud, focusing on structure

Good prep resources

• Grokking the System Design Interview
• McKinsey Digital or QuantumBlack tech blogs
• General SWE system design interview videos (not pure LeetCode)

Three days is tight, but you can still prepare well if you focus.

Here's what you can expect:

McKinsey SWE interviews are different from standard consulting cases. You'll likely get a mix of technical problem-solving, system design or architecture questions, coding or logic-based problems, and behavioral questions about teamwork and communication.

The problem-solving part usually focuses on product or technical scenarios. Think: how would you design a system, debug an issue, or improve a technical product. Less "should the client enter a new market" and more "how would you build this or fix this."

Here's how I'd use the 3 days:

• Day one: Understand the format. Search for McKinsey Digital or McKinsey SWE interview experiences on Glassdoor and Blind. Read 5-10 recent ones and note the patterns. Also review basic system design concepts like scalability, databases, APIs, and trade-offs between approaches.
• Day two: Practice technical problem-solving. Do 3-5 LeetCode medium problems. Focus on explaining your thinking out loud, not just solving silently. Also practice one system design question like "Design a URL shortener" or "Design a notification system." Talk through your approach step by step.
• Day three: Simulate the interview. Do a mock with a friend or out loud by yourself. Practice explaining technical concepts simply. McKinsey cares about communication, not just correctness. Also prepare 2-3 behavioral stories: a time you solved a hard technical problem, a time you worked with non-technical people, and a time you dealt with conflict or ambiguity.

A few things to keep in mind:

Think out loud. They want to see your reasoning, not just the answer. Keep it structured. Even for technical problems, break it down into steps. Don't overcomplicate. Simple and clear beats complex and confusing. Ask clarifying questions. It shows you think before jumping in.

You've got this. Focus on the basics and communicate clearly.

Hi,
If you're interviewing for a client-facing SWE role, the problem-solving interview is going to be the same type of case interview as for consulting roles. They want you to be able to break the problem into MECE parts, demonstrate calculations, and show analytical thinking. This interview likely will have no PEI part, as PEI for SWEs is different and typically your hiring manager assesses it. I have interviewed SWEs when I was a manager at McKinsey.
As for prep, go to the official McKinsey website and read through their cases / watch videos. You're going to get a case similar to the one shows. Then you can browse interviwer-led cases here on prep lounge. If you'd like, happy to also do a mock interview with you here.
For internal SWEs, I believe there is no problem solving interview / no case study.

Kateryna

Hi there,

McKinsey software engineering interviews are quite different from consulting case interviews. For an SWE role, you should expect technical problem-solving cases, not business cases.

Typically, the interviews include:

• Coding / algorithmic problem solving, similar to LeetCode-style questions (arrays, strings, hash maps, recursion, basic data structures)
• System design or architecture discussions, especially for anything beyond entry level (how you’d design a scalable service, trade-offs, APIs, data flow)
• Problem-solving scenarios, where you’re given a technical challenge and asked to reason through solutions, edge cases, and optimizations
• A behavioral / collaboration component focused on teamwork, ownership, and how you approach ambiguous technical problems

Where to prep in 3 days:

• Focus on core data structures and algorithms (arrays, hash maps, stacks, queues, basic graphs)
• Practice on LeetCode (Easy–Medium) or HackerRank, prioritizing speed and clean explanation
• Review system design basics (high-level design, scalability, trade-offs) even if it’s light
• Practice explaining your thinking out loud, as McKinsey cares a lot about structured communication, even in technical roles

Avoid business case prep — it won’t help here. The biggest differentiator is clear reasoning, clean code, and structured explanation under pressure.

If you want, I can help you prioritize exactly what to focus on in the next 72 hours based on your level.

Best,
Evelina