---
title: "Discussion on \"How to notify 50 million users about a flash sale: pull, push and FCM topics\" | Hashnode"
description: "Discussion on \"How to notify 50 million users about a flash sale: pull, push and FCM topics\". The sale starts at 12:00. Marketing wants all 50 million users to know, and most of them have the app closed.\nYour server can't call a phone, and 50 million is a lot of phones to reach in one minute."
url: "https://hashnode.com/posts/flash-sale-push-notifications-fcm-topics/6af6762a23037bb26d250a7e"
---

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# [How to notify 50 million users about a flash sale: pull, push and FCM topics](https://systemdesignwithparam.hashnode.dev/flash-sale-push-notifications-fcm-topics?utm_source=hashnode&utm_medium=feed)

The sale starts at 12:00. Marketing wants all 50 million users to know, and most of them have the app closed. Your server can't call a phone, and 50 million is a lot of phones to reach in one minute.

2d ago · 7 min read · systemdesignwithparam.hashnode.dev  
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-   [#system-design](https://hashnode.com/tag/system-design)
-   [#system-design-interview](https://hashnode.com/tag/system-design-interview)
-   [#push-notifications](https://hashnode.com/tag/push-notifications)
-   [#firebase](https://hashnode.com/tag/firebase)
-   [#backend](https://hashnode.com/tag/backend)

## Written by

[Parminder singh](https://hashnode.com/@param007)

@param007

  
[View profile](https://hashnode.com/@param007)

Software developer · Writing system design with real numbers and tests

Software developer who writes about system design the practical way. I take interview-style questions like rate limiters, flash sales, and large file uploads, then test them on my own machine and share what actually breaks. New post every few days at System Design with Param.

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