Faster Sync with HikariCP in SymmetricDS Pro 3.17.3

SymmetricDS Pro 3.17.3 introduces HikariCP as an available connection pool alongside DBCP2 — and the performance difference is significant. Here’s what changed, why it matters, and what our benchmarks showed.

What is a database connection pool and why does it matter?

Every time SymmetricDS syncs data, it borrows a database connection from a pool, does its work, and returns it. That borrow-and-return cycle happens thousands of times per minute in an active deployment — and the speed of the pool itself directly affects how fast your data moves. Apache DBCP2, the connection pool SymmetricDS has shipped with for years, was built for a world where connection management was a secondary concern. HikariCP was built with one goal: make that borrow-and-return cycle as fast and as safe as possible, at any concurrency level.

How does HikariCP differ from DBCP2?

The architectural difference shows up most clearly under load spikes — exactly the workload SymmetricDS generates. When a burst of sync requests hits a DBCP2 pool, it reacts by spawning new connections eagerly: one per request, each taking 150ms or more to establish. HikariCP takes the opposite approach. It queues waiting threads on the pool itself and reuses connections as they become free, only opening new ones when genuinely necessary. According to HikariCP’s own published benchmarks, this approach handles spikes with 85–90% fewer new connections than DBCP2 and completes the same burst of work 8–9x faster. For SymmetricDS customers running dozens or hundreds of nodes against a shared database, fewer connections means less contention, less overhead on the database server, and more headroom for the rest of the application.

How much faster is HikariCP in practice?

We tested this directly against a live SymmetricDS Pro 3.17.3 environment running a pipeline mirroring topology on PostgreSQL 18. With both pools configured at equivalent sizes — 20 and 50 connections — HikariCP delivered 20–25% higher throughput and cut p99 latency (the worst 1-in-100 response time) roughly in half: from 36ms down to 16.5ms at 20 connections, and from 26ms down to 15.5ms at 50. That latency gap matters because p99 is what your slowest nodes feel — and in a large sync network, the slowest nodes are the ones that generate issues.

How do you enable HikariCP in SymmetricDS Pro 3.17.3?

Starting in SymmetricDS Pro 3.17.3, HikariCP is available as a feature alongside DBCP2. For most deployments, switching requires only a few small configuration tweaks — no code changes, no schema changes. Customers with straightforward setups will see the improvement immediately; those running large multi-engine deployments or connecting to heavily-loaded customer databases will see the biggest gains, since those are exactly the scenarios where DBCP2’s eager connection spawning and lock-based internals create the most pressure.

Ready to see the difference in your own environment? Start a free trial of SymmetricDS Pro or talk to our team to find the right configuration for your deployment.