Neon has introduced an automatic scaling feature for its Postgres instances to keep the working set in memory. The working set size is estimated using HyperLogLog (HLL), a probabilistic algorithm that estimates the cardinality of a set with high accuracy and minimal memory usage. By dynamically estimating and adjusting the working set size, Neon can provide significant speed-ups for real-world workloads while ensuring predictable performance. The new feature is expected to be more cost-efficient than fixed-size nodes with the same performance.