Loading…
Design a Distributed Email Service is a hard system design interview question covering Distributed Systems, storage, queues, databases — the kind asked at FAANG (Facebook/Meta, Apple, Amazon, Netflix, Google) and AI-first companies like Anthropic, OpenAI, and Nvidia.
Design an email service like Gmail or Outlook at consumer scale: 1 billion users, each receiving about 40 emails and sending about 10 per day, interoperating with the entire internet over SMTP. Support spam filtering, attachments, multi-device sync, and mail kept forever unless deleted. Once your servers accept a message, it must never be lost, and duplicates must never appear in a mailbox.
Interactive walkthrough on Pro
Upgrade to Pro to unlock the clarifying questions, architecture, capacity calculations, tradeoffs, follow-up answers, and the model answer.
What's inside this guide
Design rounds are decided on capacity estimates. Both tools are free.
Fully unlocked, no account needed — solutions, walkthroughs and follow-up answers included.
Or start the Study Plan — a week-by-week order for your loop, and week 1 is entirely free.
A full interview loop is more than one round. These are the others, each with what is on the site for it.