Consistent Hashing, Actually Working: From Modulo to a Java Ring with Virtual Nodes
“Design a distributed cache.” You say hash(key) % N. The interviewer nods, then asks: “A node dies at 3 AM. What happens?” If your answer is “we rehash everything,” you’ve just told them your cache has a planned outage every time the cluster changes shape. This post builds the real answer — a working consistent hash ring in Java, with virtual nodes and tests — and the lineage and follow-ups that turn it into a senior-level answer. ...