A 45 to 60 minute round where you design a system out loud and defend the trade-offs. Here is what it tests, how it differs from LLD, and how it is scored.
HLD stands for High Level Design. In an HLD round an interviewer gives you a deliberately vague problem - design WhatsApp, design a ticket booking system - and you have 45 to 60 minutes to turn it into an architecture out loud. There is no single correct answer and no compiler to tell you that you are wrong. What is being graded is the reasoning you narrate on the way to a design, which is why it feels so unlike a coding round to anyone sitting it for the first time.
The round almost always follows the same arc, even when the interviewer never says so. You establish requirements and scale before drawing anything, sketch a component diagram, then get pushed: what breaks at ten times this traffic, which database and why not the other one, what happens when this component dies, what are you trading away for that consistency guarantee. Candidates who jump straight to boxes and arrows without pinning down requirements lose the round in the first five minutes, regardless of how good the final diagram looks.
It is a distinct round from LLD, and the two are usually scheduled separately. High level design is about how many services hold together under load - partitioning, replication, caching, queues, failure modes. Low level design is about how one service is structured internally - classes, responsibilities, and whether the model absorbs a new requirement without a rewrite. Being strong at one predicts very little about the other, which is why product company loops test both.
5-10 min
Functional and non-functional requirements. What is in scope, what is explicitly not, and who the users are. Skipping this is the most common way the round is lost.
5 min
Daily active users, reads per second, storage growth. Rough numbers are fine; having none is not - they drive every decision that follows.
10-15 min
Services, data stores, queues and the paths between them. Breadth first, then depth where the interviewer pushes.
15 min
One or two components examined properly: schema, partitioning, cache strategy, consistency model. This is where most of the score is decided.
5-10 min
What breaks first under load, what happens when a component dies, and how the system degrades rather than collapses.
High Level Design. In interview scheduling it is often used interchangeably with "system design round". Some companies call it the architecture round; the content is the same.
HLD is about how multiple services hold together under load - partitioning, replication, caching, queues and failure modes. LLD is about how one service is built internally - classes, responsibilities, design patterns and whether the model absorbs a new requirement cleanly. They are usually separate rounds, and strength in one does not predict strength in the other.
No, and interviewers are not looking for one. Two candidates can reach different architectures and both score well if each can say why they chose it and what it costs. What loses the round is a design presented without trade-offs, or one that cannot answer what happens when traffic grows tenfold.
Typically on requirement gathering, architecture, data modelling, scalability reasoning and communication. Communication carries more weight than candidates expect: an interviewer can only grade the reasoning you say out loud, so a strong design explained silently scores worse than a simpler one explained well.
Rarely in campus drives, which weight DSA and fundamentals. It appears for off-campus product company applications and becomes standard from SDE-2 upward. If you are targeting product companies, it is worth preparing before you are formally expected to know it.
Six to eight weeks of consistent work gets most engineers to a competent level, assuming they already build software professionally. The bottleneck is rarely reading - it is practice speaking a design out loud under time pressure, which is a separate skill from recognising a good architecture on a page.
Reading about the round is not the same as sitting it. Practise a real design out loud and get scored on it.