Common tools for diagramming system design interviews — and how to use them

When you’re in the middle of a system design interview, the last thing you want is to get tripped up by the tool you’re using. Diagramming is a critical part of communicating your thought process, and using the right platform can make or break your ability to convey ideas clearly and confidently.

In this guide, we’ll walk through some of the most commonly used whiteboarding tools for interviews — what they do well, what to watch out for, and how to get comfortable with them before your interview day.

Why the tool you use matters

In most interviews, you won’t be tested on your diagramming software skills, but the tool still matters. A clunky interface, unfamiliar keyboard shortcuts, or poor formatting options can slow you down and distract from the ideas you’re trying to express.

That’s why it’s important to:

• Ask in advance what tool will be used in the interview.
• Practice using that tool before the interview.
• Default to a tool you’re comfortable with when given a choice.

Let’s take a look at the most common tools engineers use to diagram during interviews.

Excalidraw

What it is: A simple, open-source virtual whiteboard that feels like sketching on paper. Excalidraw is designed to mimic the experience of drawing on a physical whiteboard and is especially popular among engineers who value speed and simplicity.

Pros:

• Lightweight and intuitive — easy to get started with
• Supports freeform drawing, shapes, connectors, and text
• Local-first and privacy-focused
• Popular with companies like Meta and other Big Tech interview loops

Cons:

• Minimal formatting options
• No built-in collaboration unless used with plugins or Excalidraw+ (the paid version)

Practice tips:

• Try creating a basic system diagram using just shapes and arrows
• Use the shortcut menu to speed up shape placement
• Practice drawing workflows, data pipelines, or infrastructure layers to simulate real design scenarios

FigJam (Figma)

What it is: A collaborative whiteboarding tool built by the Figma team. FigJam is part of the broader Figma design ecosystem, offering a visually polished and feature-rich interface. It’s a favorite among candidates who want their diagrams to be clean, professional, and presentation-ready.

Pros:

• Highly polished interface with strong UX
• Easy to group and align shapes and components
• Real-time collaboration support
• Useful for diagrams that require clarity and structure

Cons:

• Slightly heavier and more design-focused than other tools
• May require a Figma account to access full features or save work

Practice tips:

• Explore the shape and connector libraries to develop a reusable system design layout
• Use sticky notes or annotations to highlight tradeoffs, performance considerations, or failure modes
• Test presenting your diagram in fullscreen mode to simulate walking an interviewer through your solution

TLDraw

What it is: A lightweight, browser-based diagramming tool that’s gaining popularity, particularly for quick sketches or when performance is more important than polish. TLDraw is ideal for practicing without any login or account setup.

Pros:

• Extremely fast to load and start using
• Simple UI with helpful keyboard shortcuts
• Great for low-fidelity visuals and quick iterations

Cons:

• Limited formatting and collaboration capabilities
• Text alignment and layering can be tricky compared to other tools

Practice tips:

• Use TLDraw when you want to rapidly explore multiple architectural variations
• Focus on the structure and communication of your ideas, not polish
• Try using one canvas for multiple ideas and transitions, like a storyboarding approach

Google Slides

What it is: A familiar presentation tool that many candidates already know and use. While not built specifically for diagramming, Google Slides offers precision and formatting features that can be leveraged for clean, structured diagrams.

Pros:

• Excellent text and shape formatting
• Precise alignment and organization tools
• Easy to share and collaborate in real time

Cons:

• Not purpose-built for technical diagramming
• Can feel too formal or slow for fast-paced interview environments

Practice tips:

• Use a blank slide for each diagram and minimize slide distractions
• Create reusable components (e.g., a database box or service icon) and copy them between slides
• Use connector lines and grouping features to create clean, layered diagrams that stay organized

Choosing the right tool for you

There’s no one-size-fits-all answer. The best tool is the one that helps you think clearly and communicate efficiently under time pressure. If your interviewer allows you to choose, go with the one you’ve practiced in the most.

If a tool is assigned, spend time practicing the fundamentals: drawing shapes, connecting components, and organizing space in a way that’s easy to follow.

Final tips

Diagramming tools aren’t just about aesthetics—they shape how you think, explain, and adjust your solution on the fly. Whether you’re working on a clean architecture diagram or sketching out a rough workflow, the way you use the tool should help the conversation, not complicate it.

Here are a few tips that apply across all platforms:

• Get comfortable with keyboard shortcuts: Speed matters, and being fluent with basic actions (like creating shapes, connecting elements, or duplicating objects) lets you stay focused on the content of your solution.
• Stick to simple shapes and clear labels: Boxes for services, circles for users, and diamonds for databases are a common convention. Consistency goes a long way in helping the interviewer follow your logic.
• Make your diagram readable: If you were to send a screenshot of your diagram without explanation, could someone else follow what you were proposing? Use alignment, spacing, and basic grouping to keep things visually tidy.
• Practice under light time pressure: Try giving yourself 25–30 minutes to go from prompt to diagram, just like in a real interview. Practicing the full workflow helps you build pacing and flow.
• Narrate as you diagram: In the interview, you’ll be talking and diagramming at the same time. Practicing both together helps you sound confident and structured when it counts.

The more you practice with these tools in real-world scenarios, the more natural whiteboarding will feel, turning it from an interview hurdle into a clear strength. When diagramming becomes second nature, it stops being a hurdle and becomes a strength. With the right tools — and a bit of practice — you’ll be ready to lead the conversation in any system design interview.

Get holistic interview prep with Formation

The Formation Fellowship gives mid-level and senior engineering job seekers everything they need to land their dream roles — including personalized skill brush-ups, resume help, unlimited mock interviews with experienced software engineers and hiring managers from top-tier tech companies, career and negotiation support, and more. 

If you’re having trouble navigating your job search on your own, apply here and get unconditional support from a team of engineering mentors, technical recruiters, career coaches, and more.