if (buffer.refCnt() > 0) buffer.release() is a recurring call across the code base. Care to add a ReferenceCountedUtil to the io.r2dbc.mssql.util package that would cover instance-of check (passing in an Object), catering for nullability and having the refCnt() check?

Sure I can move it, the it would look like:

public class ReferenceCountedUtil {

    public static boolean safeRelease(ByteBuf buffer) {
        if(buffer.refCnt() > 0){
            return buffer.release();
        }
        return false;
    }

}

I don't understand why we to pass it as Object since all these checks are done for ByteBuf type.

Additionally there is io.netty.util.ReferenceCountUtil#safeRelease(java.lang.Object) which seems to do some magic around releasing the buffer in safe mode. However I don't want to decrease performance by making so many count check:

public final boolean release(T instance) {
    int rawCnt = nonVolatileRawCnt(instance);
    return rawCnt == 2 ? tryFinalRelease0(instance, 2) || retryRelease0(instance, 1)
            : nonFinalRelease0(instance, 1, rawCnt, toLiveRealRefCnt(rawCnt, 1));
}

I don't understand why we to pass it as Object since all these checks are done for ByteBuf type.

This is the design choice that netty made and there's no imminent reason to deviate or invent our own design that would introduce accidental complexity.

However I don't want to decrease performance by making so many count check:

io.netty.util.ReferenceCountUtil#safeRelease(java.lang.Object) contains flow control by exceptions and logging. I don't see the need to have multiple count checks and instanceof checks (as in ReferenceCountUtil) have a lower CPU penalty than exceptions.