Terms of Service

Last updated: February 28, 2026

1. Acceptance of terms

By accessing or using fivenines (“the Service”), operated by Firebrick Labs EOOD, a company registered in Bulgaria (UIC 208431638) with its registered address at 31 Alexander Malinov Blvd., zh.k. Mladost 1A, Sofia 1729, Bulgaria (“we”, “us”, “our”), you agree to be bound by these Terms of Service. If you do not agree, do not use the Service.

These terms apply to all visitors, registered users, and any other persons who access the Service. Our Privacy Policy and Cookie Policy are incorporated by reference.

2. Eligibility

You must be at least 16 years of age to use the Service. By creating an account, you represent that you meet this age requirement. If you are using the Service on behalf of an organization, you represent that you have the authority to bind that organization to these terms.

3. Accounts

  • You sign in via Google OAuth. You are responsible for maintaining the security of your Google account and for all activity that occurs under your fivenines account.
  • You must provide accurate information during registration and keep it up to date.
  • You may not create multiple accounts, share your account with others, or use another person's account without permission.
  • Notify us immediately at firebricklabs@gmail.com if you suspect unauthorized use of your account.

4. The Service

fivenines is a learning platform for system design. The Service includes interactive tutorials, coding challenges, architecture problems with AI-powered evaluation, community features, and leaderboards. We offer both a free tier (with usage limits) and a Pro tier (with expanded access).

Service Level Agreement: Despite our name, fivenines does not guarantee 99.999% uptime. The Service is provided without any guaranteed Service Level Agreement (SLA).

We reserve the right to modify, suspend, or discontinue any part of the Service at any time, with or without notice. We will make reasonable efforts to notify you of material changes.

5. Subscriptions & payments

  • The free tier provides limited access to tutorials, coding challenges, and architecture problems.
  • The Pro tier provides expanded access. Pricing, billing cycle, and payment terms are displayed at the time of purchase. We may change our pricing from time to time, but we will notify you in advance of any price changes affecting your subscription.
  • Payments are processed securely through third-party payment providers. We do not directly collect or store your full credit card details.
  • All fees are stated in the currency shown at checkout. Applicable taxes may apply depending on your jurisdiction.
  • Subscriptions renew automatically unless cancelled before the end of the current billing period. You may cancel at any time from your account settings.
  • Right of Withdrawal (EU/UK): By upgrading to the Pro tier, you expressly consent to receiving immediate access to the digital content and acknowledge that you thereby lose your statutory 14-day right of withdrawal. All other refunds are handled on a case-by-case basis. Contact us at firebricklabs@gmail.com for refund requests.

6. Acceptable use

You agree not to:

  • Use the Service for any unlawful purpose or in violation of any applicable laws or regulations.
  • Submit confidential, proprietary, or trade secret information belonging to your employer, clients, or any third party for AI evaluation or community publication.
  • Submit malicious code, attempt to exploit vulnerabilities, or interfere with the operation of the Service.
  • Abuse the code execution or AI evaluation features by submitting harmful, abusive, or excessively large payloads.
  • Scrape, crawl, or use automated tools to extract content from the Service without our written permission.
  • Post content in community features that is harassing, defamatory, obscene, or infringes on the rights of others.
  • Circumvent usage limits, access controls, or other restrictions on the Service.
  • Impersonate another person or misrepresent your affiliation with any entity.

We reserve the right to suspend or terminate accounts that violate these rules.

7. Intellectual property

Our content — all tutorials, problems, UI design, graphics, and underlying software are owned by Firebrick Labs EOOD or its licensors and are protected by intellectual property laws. You may not reproduce, distribute, or create derivative works from our content without permission.

Your content — you retain ownership of the architecture diagrams, code, comments, and other content you submit. You represent and warrant that you own or have the necessary rights to submit this content, and that it does not contain confidential or proprietary information belonging to your employer or any third party.

By publishing content to the community, you grant us a non-exclusive, worldwide, royalty-free license to display, distribute, and make available your published content as part of the Service. You may delete your content at any time, which will terminate this license. We do not claim ownership of your content, nor do we use your private drafts to train foundational AI models.

8. Copyright infringement (DMCA)

We respect the intellectual property rights of others. If you believe that content published on the Service infringes your copyright, please send a written notice to firebricklabs@gmail.com with the subject “Copyright Takedown.” We will respond promptly to valid takedown requests and reserve the right to terminate the accounts of repeat offenders.

9. AI-generated feedback

The Service uses third-party AI models to evaluate architecture diagrams and provide feedback. By using these features, you agree to comply with the Acceptable Use Policies of our AI providers.

AI-generated evaluations, scores, and suggestions are provided for educational purposes only and should not be relied upon as professional engineering advice. AI outputs may contain errors or inaccuracies. We do not guarantee the correctness, completeness, or fitness for any particular purpose of AI-generated content.

10. Code execution

The Service allows you to submit code for execution in a sandboxed environment. You are solely responsible for the code you submit. Do not submit code that is malicious, harmful, or designed to exploit the execution environment. We reserve the right to limit or restrict code execution at our discretion.

11. Disclaimer of warranties

The Service is provided “as is” and “as available” without warranties of any kind, whether express or implied, including but not limited to implied warranties of merchantability, fitness for a particular purpose, and non-infringement. We do not warrant that the Service will be uninterrupted, error-free, or secure.

12. Limitation of liability

To the maximum extent permitted by applicable law, Firebrick Labs EOOD shall not be liable for any indirect, incidental, special, consequential, or punitive damages, or any loss of profits or revenue, whether incurred directly or indirectly, or any loss of data, use, or goodwill, arising out of or in connection with your use of the Service.

Our total aggregate liability for all claims arising from or related to the Service shall not exceed the amount you have paid us in the twelve (12) months preceding the claim, or fifty euros (EUR 50), whichever is greater.

Nothing in these terms excludes or limits our liability for death or personal injury caused by negligence, fraud, or any other liability that cannot be excluded under applicable law.

13. Indemnification

You agree to indemnify and hold harmless Firebrick Labs EOOD, its officers, directors, employees, and agents from any claims, damages, losses, or expenses (including reasonable legal fees) arising from your use of the Service, your violation of these terms, or your violation of any rights of a third party.

14. Termination

  • You may delete your account at any time from Settings › Privacy & Data. This permanently removes your account and all associated data.
  • We may suspend or terminate your account if you violate these terms, with or without prior notice depending on the severity of the violation.
  • Upon termination, your right to access the Service ceases immediately. Sections that by their nature should survive termination (including intellectual property, limitation of liability, indemnification, and governing law) will survive.

15. Governing law & disputes

These terms are governed by and construed in accordance with the laws of Bulgaria, without regard to conflict of law principles.

Any disputes arising from or relating to these terms or the Service shall first be attempted to be resolved through good-faith negotiation. If a dispute cannot be resolved amicably within 30 days, either party may pursue resolution through the competent courts in Sofia, Bulgaria.

If you are a consumer in the EU, you retain the right to bring proceedings in the courts of your country of residence, and nothing in these terms affects your statutory consumer rights under applicable EU law. You may also access the European Commission's Online Dispute Resolution platform at http://ec.europa.eu/odr.

16. Changes to these terms

We may update these terms from time to time. Material changes will be communicated via email or an in-app notice at least 30 days before they take effect. Continued use of the Service after changes take effect constitutes acceptance of the revised terms. If you do not agree with the revised terms, you should stop using the Service and delete your account.

17. Contact

If you have questions about these terms, you can contact us at: