You can test this yourself, I wouldn't recommend trying it on a busy server.
Could something be put in place to prevent such a simple task causing lag?
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 387ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 391ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 394ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 400ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 404ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 408ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 412ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 421ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 419ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took average 5471ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 423ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 428ms
Calling 'cmdChangeElement' on 'ServerRewards v0.4.73' took 437ms