System design notes
System design notes, with the diagram right beside them.
Capacity math, trade-offs and the architecture diagram belong on one page. Write on the left, draw on the right, and drag the diagram into the write-up.
How it works
Sketch the architecture
Draw boxes and arrows by hand; auto-shape snaps them into clean shapes and connected arrows on an infinite canvas.
Write the trade-offs
Explain each component next to the drawing, with LaTeX for back-of-envelope numbers and Mermaid for request flows.
Keep them in sync
Group the diagram as a figure and drag it into the note. Change the canvas later and the note updates.
Real examples
Questions
Is it good for interview prep?
Yes. Keep one project per design — note and diagram together — in a notebook, and review them on any device.
Can I generate the diagram from text?
Yes. Write a Mermaid flowchart in a note, or let the octonote CLI turn it into real, editable shapes on a canvas.
Can I share a design with my team?
Share it by email as an editor or viewer, open it to anyone with the link, or publish it as a public page.
More: Notes with math and Mermaid · Technical explainers · Publish notes as a website · Notes and diagrams for Claude Code · Use with Claude Code and Codex
Start your first one free.
Free to start. No credit card, no password.