Best Platforms to Practice System Design Interviews

There is no single best platform for system design practice, because the round needs four different things: a course that shows the method, a human who interviews you, a drawing tool, and a list of questions. A plan that works takes one item from each category. This page compares the named options in each one, gives a cost band for each, and ends with a 45-minute practice routine.

The comparison covers system design only. If you came here for websites to practice coding problems, that question is answered in Which coding platform is best?.

Structured courses with question walkthroughs

A structured course teaches the method: collect requirements, estimate load, draw a high-level design, and go deep on one part. The value is in the walkthroughs. A full question such as a URL shortener or a news feed is solved step by step, with the reasoning written out.

Grokking the System Design Interview on this site is a paid course built around walkthroughs of the most common interview questions. Each one starts from requirements and ends with a deep dive. The course is at Grokking the System Design Interview.

System Design Primer is a free, open-source repository on GitHub. It covers the fundamentals with diagrams and links to source material, and it includes several worked questions. It has no exercises or grading. It works best as reading before a course or beside one.

ByteByteGo offers a paid course and a newsletter with a free tier. Its strength is illustrated explanations of how real systems are built. That supports the interview method but does not replace practicing questions under time.

Mock interviews with a human interviewer

A mock interview is a timed practice round with a person who asks the question, pushes back on your choices, and grades you afterward. It is the only category that tests what a course cannot. That is explaining a design out loud while someone interrupts.

Design Gurus mock interviews pair you with an engineer for a full system design round with written feedback. Sessions are booked at mock interviews. interviewing.io runs anonymous paid sessions with engineers from large companies and records each session for review. Peer practice sites match two candidates who take turns as interviewer and candidate. They are free, and the feedback quality depends on who you are matched with.

Drawing tools for practice

Most remote rounds use a shared drawing tool, so it should be one you can use without thinking. Excalidraw is free, runs in the browser, and produces simple hand-drawn shapes that are fast to place. draw.io is also free and has ready-made shapes for servers, databases, and queues. A plain whiteboard is right for on-site rounds. It is also the best way to practice drawing while you talk.

Which tool a given company uses, and how to prepare for each, is covered in What software to use for system design interview?.

Free question lists

A question list tells you what to practice. The answers section of this site has a page of system design questions for each large company. The same questions repeat across companies with small changes in scale. Pick one question per session and work it fully rather than reading twenty.

Quick comparison

A 45-minute practice routine

Take one question per session and set a timer for 45 minutes, which is the length of most real rounds. Spend the first 5 minutes on requirements. State what the system must do, how many users it serves, and which quality matters most, such as low latency or never losing a write. Spend the next 5 minutes on estimates, such as requests per second and storage per year. Those numbers decide whether you need one database or a sharded one.

Spend 15 minutes on the high-level design, drawn in the tool you will use in the real round. Spend the last 20 minutes going deep on one part, for example the cache, the queue, or the data model. Name the trade-off you are making. When the timer ends, grade yourself against a written solution and note what you missed. The missed items are the next session's plan.

Doing this alongside coding practice is a scheduling problem of its own. Preparing for System Design Interviews Alongside Coding Interview Prep gives a weekly split that fits both.

How to Prepare

• Take one item from each category. A course for the method, a question list for material, a drawing tool for fluency, and at least two mock interviews before the real one.
• Learn the fundamentals before the walkthroughs. If terms such as replication, sharding, and consistent hashing are new, Grokking System Design Fundamentals covers them first. The order is explained in Grokking System Design Fundamentals vs. Grokking the System Design Interview: Which Should You Take First?.
• Practice out loud. Reading a walkthrough is not practice. Draw and speak the design as if someone were listening. Record yourself once to hear where you stall.
• Keep a written record of each session. One page per question, with the design, the deep dive, and what the written solution did differently. That makes improvement measurable.