API Used for Facebook Messenger

Requirements

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Design of Facebook Messenger

Functional Requirements for Facebook Messenger:...

Communication Protocol for Facebook Messenger

Now let’s discuss the overall architecture of the app. Specifically, let’s see how we can send messages from one user to another:...

API Used for Facebook Messenger

What happens when user A sends a message to user B? What we require is that the user sends a message to the server and the server relays that message instantly to the user that it’s intended for. However, this way breaks the model of how HTTP requests work on the internet because they can’t be server-initiated rather they have to be client-initiated. So this isn’t going to work and we need to come up with something else....

Database Design for Facebook Messenger

Here we are taking only three API servers but in a real system, when we are trying to support hundreds of millions of users, we will need hundreds or thousands of API servers to support the huge amount of requests as one API server can handle only thousands of requests at a time....

Data Types

We still need to think about how we are going to store and persist these messages in our database When we think about what kind of database to choose for application, According you our requirements we know that we want to support a really large volume of requests and store a lot of messages. We also care a lot about the availability and uptime of our service so we want to pick a database that is going to fit these requirements....

Scalability for Facebook Messenger

So, how we are going to store and model this data in our database. We know we’re going to need a few key tables and features like users, and messages and we are also going to probably need this concept of conversations, which will be groups of users who are supposed to receive messages....

Conclusion

So in particular, one thing we are thinking about is the cost of going to our database and retrieving messages from it repeatedly so one thing we would like to add to the architecture is some sort of caching service or caching layer which would be like a read-through cache....