As mentioned by Slugart, it is best to benchmark and go from there.
That being said, there are a few things you can do if you find the performance to be a bottleneck:
- Lower the number of messages - generally, 20 messages per second per client might be a bit too much - games usually go with less than half of that (6-12 msg/s).
- Use binary format instead of json - if the server needs to act as a relay, you could encode your messages using binary protocol. Look into protobuf or messagepack.
There are some other options available, but they are not available for javascript (as far as I know).
In case you are expecting a large number of players, and every want to optimize as much as possible, I would suggest switching to a backend that supports multithreading, object pooling (to reduce Garbage Collection time), etc, to gain the most performance.
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