Does running a full node make rpc calls faster? Hello I am running a pruning node on my VPS, and some of the RPC calls such as get balance take minutes to load. I need to check the balance every time the users access the website. I was wondering if running a full node would make these RPC calls faster. 

The time command shows that bitcoin-cli is taking long due to I/O operations. What could I do?

~$time bitcoin-cli getbalance profit
0.00000000

real    6m16.762s
user    0m0.000s
sys     0m0.000s
This has nothing to do with pruning.  RPC calls like getbalance only use data stored in the wallet and/or UTXO database.  They don't have any need to refer to the archive of old blocks, and having it available wouldn't help anything.

VPSs often don't have a lot of RAM, and bitcoind in its default configuration needs a lot - say a gigabyte or more.  Is it possible that you're short on physical memory and therefore having to swap?  This can make a system very slow.  You can reduce bitcoind's memory usage somewhat with different options (see How to run bitcoind in a low memory environment) but you may also have to configure your VPS with more memory (and pay more).

Another possibility is that your server is overloaded with other tasks.

Either way, running top will probably reveal something.