What is a read/write quorum?

N, W, R = 5, 3, 3   # W + R > N guarantees overlap

replicas = [{"value": None, "version": 0} for _ in range(N)]

def write(value, version):
    acks = 0
    for r in replicas:               # send to all, succeed once W ack
        r["value"], r["version"] = value, version
        acks += 1
        if acks == W:
            break
    return acks >= W

def read():
    sample = replicas[:R]            # read from R replicas
    latest = max(sample, key=lambda r: r["version"])  # newest wins
    return latest["value"], latest["version"]

write("v2", 2)
print("read ->", read())   # sees v2 because the read/write sets overlap