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The Framework proposed in this space (Alex Xu) is applied to propose a design : Getting started - a framework to propose... |
Introduction
A notification alerts a user with important info like events, … It’s more than just mobile push notifications.
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There are 3 types of notification formats are : mobile push notification, SMS message and Email
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Step 1 - Understand the problem and establish the scope
Types of notifications to support ? | Push notifications, SMS Message and Email |
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Real-time System ? | Real-time, but a delay is acceptable. |
Supported devices ? | iOS devices, android devices and laptop/desktop. |
Triggers ? | Triggered by client app and scheduled on the server-side. |
Users be able to opt-out ? | Chose to opt-out means no longer receive notifications. |
How many notifications per day ? | 10 million for Mobile push notif., 1 million for SMS, 5 millions for emails. |
Step 2 - High-level design
No need to propose a high-level design with a single server setup because of the following reasons :
One single notification server, so a single point of failure.
Challenging to scale (limitations).
Processing and sending notifications could be resource intensive.
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Step 3 - Design deep dive
Reliability
Purpose is to show additional components : notification template, rate limiting, retry mechanism… One of the most requirements is to prevent data loss with a retry mechanism and notification log.
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The notification servers are equipped with 2 features : authentication and rate-limiting.
A retry mechanism to handle notification failure : retry for a predefined number of times.
Worker will process from a notification template to be more efficient.
To prevent data loss, data will be stored as log.
Step 4 - Pros & Cons
Pros
Retry mechanism to minimize the failure rate;
User Info DB used as User Setting to help user to opt-out of receiving notifications;
Rate limiting helping to control the frequency.
Cons
Multiple queue (for each provider) to maintain and to manage.