Why ScyllaDB’s Shard Per Core Architecture Matters

ScyllaDB's shard-per-core architecture is a distinctive feature that contributes to its predictable performance at scale, as explained through various perspectives including those of its co-founder Dor Laor, power user Bo Ingram, and VP of Product Tzach Livyatan. Introduced in 2015, this architecture allows for independent, lock-free processing across server cores, with each shard having its own CPU, memory, and network resources, thus eliminating contention and enabling linear scalability as server cores increase. Bo Ingram highlights that this approach provides predictable low latencies and compares favorably against systems like Cassandra, which shard only per node, often leading to cluster-wide performance issues. Tzach Livyatan further elaborates on how this design avoids resource competition common in thread-pool-based systems, ensuring high throughput and low latency by allowing each core to operate independently without context switching. The article creatively uses the analogy of puppies fighting over food bowls to illustrate the benefits of the shard-per-core architecture, emphasizing the efficient resource allocation that avoids contention, much like how each puppy gets its own bowl of food without competition.