it is 1 thread so have queue size that mostly do not require to queue

jobs on caller

src/main/java/com/zaxxer/hikari/pool/HikariPool.java

@@ -117,7 +117,7 @@ public class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateL
 
       ThreadFactory threadFactory = config.getThreadFactory();
       this.addConnectionExecutor = createThreadPoolExecutor(config.getMaximumPoolSize(), poolName + " connection adder", threadFactory, new ThreadPoolExecutor.DiscardPolicy());
-      this.closeConnectionExecutor = createThreadPoolExecutor(1 + (config.getMaximumPoolSize() / 2), poolName + " connection closer", threadFactory, new ThreadPoolExecutor.CallerRunsPolicy());
+      this.closeConnectionExecutor = createThreadPoolExecutor(config.getMaximumPoolSize(), poolName + " connection closer", threadFactory, new ThreadPoolExecutor.CallerRunsPolicy());
 
       if (config.getScheduledExecutorService() == null) {
          threadFactory = threadFactory != null ? threadFactory : new DefaultThreadFactory(poolName + " housekeeper", true);