Database / ScyllaDB Interview questions
How is data replicated across nodes in ScyllaDB?
ScyllaDB uses consistent hashing to map each partition key to a token, and that token determines a position on a logical ring of token ranges spread across the cluster's nodes. Each token range is owned by a set of replicas equal to the table's replication factor, with the specific placement strategy (e.g. NetworkTopologyStrategy) controlling how replicas are spread across datacenters and racks.
CREATE KEYSPACE ecommerce WITH replication = { 'class': 'NetworkTopologyStrategy', 'dc1': 3, 'dc2': 3 };
A write is sent to all replicas responsible for its token range in parallel, and the client's requested consistency level determines how many acknowledgments must return before the write is considered successful. This peer-to-peer replication model, with no single master, means any replica can accept a write or serve a read, which is central to ScyllaDB's high availability - there's no single point of failure the way a primary/replica relational system has.
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