Privacy Policy

1. Introduction

Complete System Design (“we”, “our”, or “us”) respects your privacy and is committed to protecting your personal data. This privacy policy explains how we collect, store, process, and safeguard your information when you visit and use completesystemdesign.dev and associated subdomains.

2. Data We Collect

We only collect the minimum information strictly necessary to provide the curriculum experience:

• Account Identification: When you sign in via Google OAuth, we receive your name, email address, and profile avatar URL. We never receive or store your Google password.
• Curriculum Progress & Learning State: Your completed topics, quiz scores, custom notes, saved bookmarks, and highlighted passages. This data is synced to your account or stored in your browser's local storage.
• Payment Information: All transactions are processed through our PCI-DSS Level 1 certified payment processor (Dodo Payments / Stripe). We never store or see your raw credit card numbers or banking credentials.
• Usage Telemetry: Anonymized crash reports, browser user-agent, and technical performance metrics to ensure low-latency delivery of diagrams and interactive simulators.

3. How We Use Your Information

• To provide authenticated access to the 280 curriculum topics, diagrams, and 280 interactive simulators.
• To synchronize your reading bookmarks, highlights, and milestone badges across desktop and mobile devices.
• To deliver transactional receipts and lifetime access confirmations.
• To prevent fraudulent chargebacks and enforce fair-use limits.

We never sell, rent, or trade your personal data or email address to third-party advertisers.

4. Cookies & Local Storage

We utilize browser LocalStorage and essential session cookies strictly for retaining your theme preferences (Dark / Light mode), your active study track, and your offline reading state. We do not use third-party cross-site advertising cookies.

5. Data Retention & Your Rights

You maintain full ownership of your data. You may request complete export or permanent deletion of your account and saved notes at any time by contacting our engineering team at contact@completesystemdesign.dev.

6. Security Measures

All traffic between your browser and our edge servers is encrypted via TLS 1.3 with HSTS preloading. Database storage is encrypted at rest using AES-256 standards.

7. Contact Information

If you have any questions or data requests regarding this Privacy Policy, please email us at: