Add "Spike Arrest" policy to PROXY_REQ_FLOW-PreFlow.
Setting = 30pm (mean 30 call per minute == Rate of one call per 2 seconds)
Setting = 10pm (mean 10 call per minute == Rate of one call per 6 seconds)

Allowed rate: ps or pm

Reference:
https://help.sap.com/docs/integration-suite/sap-integration-suite/spike-arrest