Abstract: Methods and systems for out-of-application bytecode instrumentation and performance monitoring of applications, such as globally-distributed applications, decouple (1) acquiring measurements through sensor execution at applications; (2) instrumenting application bytecode with sensor bytecode and buffering and sending measurements at collector nodes; and (3) controlling instrumentation and correlating measurements at a central monitoring node. Collector nodes and applications may employ secured, high bandwidth network connections (e.g., a typical LAN connection). Collector nodes and the central monitoring node may employ non-secured, lower-bandwidth network connections (e.g., a typical WAN connection) and may use encryption and/or compression without burdening the monitored application. Multiple parallel instrumentation engines in collector nodes eliminate the possible instrumentation bottleneck presented by one centralized instrumentation engine in a single server.