// Backpressure support
    private final boolean backpressureEnabled;
    private final int maxConcurrentRequests;
    private final Semaphore requestSemaphore;
    private final AtomicInteger activeRequests = new AtomicInteger(0);
    private final AtomicLong totalBackpressureRejections = new AtomicLong(0);

    // Enhanced metrics
    private final AtomicLong minResponseTime = new AtomicLong(Long.MAX_VALUE);