Privacy policy
Last updated: October 20, 2026
qdev blitz is an interview-prep app for C++ and Python quant developer roles. This policy explains what data the app handles, why, and what you can do about it. qdev blitz is made by Velori Labs Ltd, a company registered in England and Wales (company number 17529890), which is responsible for this data ("we", "us"). Questions: lukazsdev@gmail.com.
The short version
- No sign-up: the app doesn't ask for your name or email. It works with a random ID.
- Your progress is saved on your device and backed up to our database so it isn't lost.
- Apple or Google handle payments, and RevenueCat manages subscriptions for us. We never see your payment details.
- No ads, no third-party analytics, no tracking across other apps or websites. We don't sell data.
What the app collects and why
Your learning progress
The tracks you study, your placement results, and the lessons, reviews and checkpoints you complete; your answers (the option you chose, whether it was right and how long it took); your XP, streaks, hearts and daily goal; your review schedule; and your device's time zone, so streaks follow your local day. This is stored on your device and backed up to our database under a random ID created when you start. We use it to run the app (your stats and review queue) and keep your progress safe, and we may look at answers in aggregate to find questions that are wrong or confusing.
Your subscription
If you subscribe to Premium, the App Store or Google Play takes the payment. RevenueCat, our subscription provider, receives a random app user ID, your purchase and subscription records from the store, and basic device information (such as device model, operating system, app version, country and IP address), so it can tell the app whether Premium is on. We don't receive your name, Apple ID, Google account or payment details.
Technical data
Like any internet service, our database host and RevenueCat see your IP address when the app connects, and keep it in short-lived server logs for security and troubleshooting.
Reminders
Daily reminders are scheduled on your device. Nothing about them is sent to us.
Who processes data for us
- Supabase: our database and backups, hosted in London, UK.
- RevenueCat: subscription management, in the United States.
- Apple and Google process payments under their own privacy policies.
These providers process data only to provide their service to us. Transfers outside the UK and EU are covered by standard contractual clauses.
Legal basis
If you're in the UK or EU: we process this data to provide the app you asked for (contract), and to keep it secure and working (our legitimate interests).
How long we keep it
- On your device: until you use Delete my data or delete the app.
- Backups: until you use Delete my data, or automatically after 30 days without using the app.
- Subscription records: kept by RevenueCat while needed to manage your subscription and to meet legal and accounting requirements.
Your choices and rights
You can delete your data at any time in the app: Profile → Delete my data removes it from your device and from our backup straight away. Deleting the app removes the data on your device, and an unused backup is deleted after 30 days. You can also ask us for a copy of your data, or to correct or delete it, by emailing lukazsdev@gmail.com. Because the app never asks who you are, we may not always be able to match an emailed request to your data; Delete my data always works. You can cancel a subscription at any time in your App Store or Google Play account settings.
If you're in the UK or EU, you can also complain to your data protection authority (in the UK, the Information Commissioner's Office).
Children
qdev blitz isn't directed at children under 16, and we don't knowingly collect their data.
Changes
If the way the app uses data changes, we'll update this page and the date at the top.