Privacy policy
Last updated: 22 October 2026
SDQ is a learning site for system design. This page explains, in plain words, what we keep about you, why, who helps us run the service, and how to have it deleted.
What we keep
Your email address, so you can sign in. A name, if you add one or your Google account shares it. Your onboarding answers (experience, role, goal, time zone) and settings. What you do while learning: lessons and quiz answers, challenge designs and attempts, notes, bookmarks, streaks and XP, and mock-interview conversations. Our hosting providers also keep short-lived technical logs such as IP address, browser and request times.
Why we keep it
To run SDQ: sign you in, save your progress, plan what to learn next, grade challenges and interviews, and send sign-in links. To send reminder emails, which are on by default and can be switched off with one click in any email or on your profile. To find and fix problems and make lessons better. We do not sell your data and we do not show ads.
Mock interviews and AI
When you take a mock interview, your messages and whiteboard design are sent to Anthropic (the maker of Claude) to write the interviewer’s replies and your scorecard, under Anthropic’s terms for its API. We keep the conversation so you can read your scorecard later.
Who helps us run SDQ
Vercel hosts the website. Google Cloud runs our API and keeps encrypted nightly backups, in Singapore. Neon hosts our database, in Singapore. Resend sends our emails. Anthropic powers mock interviews. Google handles “Sign in with Google” if you use it. Each only processes data to provide its service to us. If we turn on product analytics (PostHog), it uses a random id, never your email, and respects Do Not Track.
Your public progress page
Only if you switch it on, a page at a random link shows your name, level, XP, lessons and challenges done, and level certificates. It never shows your email, and search engines are asked not to index it. Switch it off at any time and the page disappears straight away.
Cookies
We use a cookie to keep you signed in and remember your light or dark theme. We use no advertising or tracking cookies.
Keeping and deleting
We keep your data while your account exists. Backups are deleted after 30 days. To get a copy of your data or have your account and data deleted, email us from your account’s address at saifmd238@gmail.com; we will do it within 30 days.
Your rights
You can ask to see, correct or delete your data, and withdraw consent (for example, to emails) at any time, as applicable laws including India’s Digital Personal Data Protection Act, 2023 allow. SDQ is meant for people aged 18 and over, or younger learners using it with a parent’s or guardian’s permission.
Changes and contact
If this policy changes in a way that matters, we will update this page and its date, and tell signed-in learners. Questions: saifmd238@gmail.com.