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ScyllaDB Admission Control Hardening

ScyllaDB Admission Control Hardening

1
posts
2026

ScyllaDB successfully mitigated performance-degrading connection storms by optimizing caching, throttling, and password hashing to achieve a 1000x reduction in tail latency. This involved improvements across the connection establishment pipeline, including connection throttling, caching of connection-related data, optimization of password hashing, and the introduction of a dedicated service level for background traffic.

2026

Cutting P99 Latency 1000X During Connection Storms by Hardening ScyllaDB Admission Control

7/1/2026

This post details the engineering efforts to harden ScyllaDB's admission control to handle connection storms. It describes the connection establishment pipeline from TCP SYN to query-ready, highlighting the introduction of throttling, caching, optimized hashing, and a dedicated service level to reduce P99 latency by 1000x during connection surges. Specific optimizations include improvements to connection throttling mechanisms, caching of connection-related data to reduce redundant work, and optimization of password hashing. The post also mentions the introduction of a dedicated service level to isolate background traffic.