I write this article to remember the different behaviour various JDBC connection pool displays when they work with slow JDBC connection(to MySQL database, in this case). It starts with a typical Java application on Spring, Hibernate, Jetty, ApacheCXF and MySQL like following code. Version 1: without correct pooling //... service code @Transactional(isolation=Isolation.READ_COMMITTED) public void foo() { //... do something with database } //... connection pool configuration ... class = "com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDataSource"; url = "jdbc:mysql://mysql.far-far-away.com/mysystem"; user = ... //... transaction management configuration in spring ... <tx:annotation-driven transaction-manager="transactionManager" order="100" /> <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory" ref="mySessionFact...