Which PSP can handle heavy volume well, especially during volatile periods?

Looking for a new PSP to replace the old one, which is starting to show problems with downtime and processing delays during very active market periods like $BTC or during strong news for $EURUSD.

I understand that nothing is perfect, but some providers have frustratingly bad latency. The main point is I want one that can handle heavy transaction loads without interruption, or at least has a clear SLA regarding uptime and throughput. Does anyone have direct experience with PSPs that handle peak volume well? I'm not looking for the cheapest fees, but rather stability and speed, because sometimes a delay of just a few seconds can cause real damage. You don't have to name them directly, just tell me what factors to look at besides commission and liquidity.