How does network latency affect performance when using synchronous replication? If a primary node fails, how long will our cluster not be reachable? How much data can be lost? Will there be any anomalies when reading from standby? We are designing our network architecture, give us a minimum RTT value for cluster solution! Many DBAs have to face these issues when designing and implementing cluster solutions. In this short talk we will tell how to quickly estimate RTT, RTO, RPO values, with the help of which Open Source tools one can test cluster solution and experimentally verify the design parameters, which metrics values can be used as a guide in design.