When I play HyPixel skywars with the replay mod installed I get lag spikes (more like freezes) that last for around half a second every 5 - 10 seconds.

I don't get these when using only OptiFine and BetterFPS and my laptop can easily run Minecraft at 60fps. Also this only seems to happen on HyPixel skywars and not any other SMP , SSP , or minigame servers.

you need to allocate more ram to mc