In some scenarios, the time that BizTalk takes to process individual messages is important, critical even. Perhaps there are users who wait for a user interface that is a thin façade over BizTalk, and the user interface blocks while it is waiting for a response message from BizTalk. Or perhaps BizTalk is deployed as a service and as such is required to meet certain service-level agreements related to message processing. Regardless of why you need to achieve low latency in BizTalk, when designing your system to meet those latency requirements, you need to be aware of the pitfalls and the proactive approaches you can adopt. This chapter discusses what low latency really means for BizTalk, how the BizTalk architecture affects latency, whether you really need low latency, and if you do, how you can tune the product to achieve low latency.