System design diagram

Sketch a system design as you would on a whiteboard: users, a CDN, a load balancer, app servers, a cache, a primary database with a read replica, and a queue with workers. It opens with that classic layout, to start from in an interview or a design review.

The usual building blocks

Load balancer: spreads requests over identical app servers, so you can add more
Cache: keeps frequently read data in memory, in front of the database
CDN: serves static files and media from close to the user
Primary database and read replicas: writes go to one, reads are spread over the others
Queue and workers: slow jobs such as emails, video or reports run outside the request
Object storage: files, uploads and backups

All of them are in the shape library, under Architecture and Databases & caches.

In an interview

Start with the simplest design that works (a client, one server, one database), then add a piece for each requirement: a load balancer for more traffic, a cache for slow reads, a queue for slow work, replicas for heavy reading. Duplicate the diagram before each step to keep the earlier versions to compare.

Write numbers on the diagram as you estimate them, such as requests per second or data per day, in notes or on the connectors.

Practise and share

Every design you practise stays in your browser under "All diagrams". Share a link to get feedback, or export an image for your notes.

Questions

Can I use it in a remote interview?

Yes, where the interview lets you use your own tool: it runs in any modern browser, with nothing to install and no account, and you can share your screen or send a link to the diagram.

Does it draw the design for me?

No. It is a drawing tool: you place and connect the pieces, starting from the example or from a blank canvas.

How is it different from an architecture diagram?

Mostly in purpose. A system design diagram is a sketch for working out how something could be built; an architecture diagram documents how a system is built. The architecture diagram page starts from a different example.