Database / ScyllaDB Interview questions
Why doesn't ScyllaDB rely on a JVM?
Cassandra runs on the JVM, which means its performance is subject to garbage collection pauses: periodically the JVM has to stop application threads to reclaim memory, and under heavy load or large heaps these "stop-the-world" pauses can spike into hundreds of milliseconds, directly hurting tail latency.
ScyllaDB was built in C++ specifically to eliminate this class of problem. Without a JVM, there's no garbage collector to pause application threads, and the Seastar framework it's built on manages memory explicitly per shard instead of relying on automatic collection. The trade-off is that C++ development is more demanding than JVM-based development, requiring careful manual memory management, but the payoff is materially more predictable p99/p999 latencies and higher achievable throughput per core, which is the core value proposition that differentiates ScyllaDB from Cassandra.
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