It depends on which performance you look at, object size always have some kind of performance implication, just to mention a few:
- Your MongoDB collection will grow, which is likely to increase your working set size, which will make your DB use more RAM, unless you go deep into MongoDB and use smart indexing and queries to counter that.
- Network traffic will increase which can be a significant cost factor, unless you can often exclude the keys you don’t need from the query, see the
selectcommand in the Parse SDKs. - In Parse Server, the de-/serialization from JSON to Parse objects take longer for large objects, this process is known to already have a significant performance impact, see this, so a larger object size is likely to increase that, but I don’t know if the increase is O(N) or more.
- If you send the whole object to the client, there is obviously another performance implication on the client side, including the data traffic for the user which can be an issue in developing countries where network data is still costly.