Is a good idea to store chat messages in a mongodb collection?

Question

I'm developing a chat app with node.js, redis, socket.io and mongodb. MongoDB comes the last and for persisting the messages.

My question is what would be the best approach for this last step?

I'm afraid a collection with all the messages like

{
    id,
    from,
    to,
    datetime,
    message
}

can get too big too soon, and is going to get very slow for reading purposes, what do you think?

Is there a better approach you already worked with?

Answer 1

In MongoDB, you store your data in the format you will want to read them later.

If what you read from the database is a list of messages filtered on the 'to' field and with a dynamic datetime filter, then this schema is the perfect fit.

Don't forget to add an index on the fields you will be querying on, then it will be reasonable fast to query them, even over millions of records.

If you would, for example, always show a full history of a full day, you would store all messages for a single day in one document. If both types of queries occur a lot, you would even store your messages in both formats.

If storage is an issue, you could also use capped collection, which will automatically delete messages of e.g. over 1 year old.