Compare runtime characteristics of JVM, V8, and CPython.

JVM (Java, Kotlin, Scala): JIT compilation (C1, C2, GraalVM), optimizing compiler, ahead-of-time possible, sophisticated GC (G1, ZGC), strong optimization (inlining, escape analysis, devirtualization). Startup overhead, warm-up time. V8 (JavaScript, Node.js): multi-tier JIT (Ignition interpreter, TurboFan JIT), hidden classes for optimization, inline caching, concurrent GC. Fast startup, optimizes hot paths. CPython (Python): interpreted (compiles to bytecode), no JIT (PyPy has JIT), GIL limits parallelism, simple reference counting + cycle collector. Alternatives: PyPy (JIT), Cython (compile to C). Each optimized for different trade-offs: JVM for long-running servers, V8 for quick response, CPython for simplicity.