Are all of your processes connecting onto the same Impala Daemon, or are you using a load balancer / varying connection options? Each Impala Daemon can only accept a finite total number of active client connections, which is likely what you are running into. Typically for concurrent access to a DB, it is better to use a connection pooling pattern with finite connections shared between threads of a single application. This avoids overloading a target server. While I haven't used it, pyodbc may support connection pooling and reuse which you can utilise via threads in python, instead of creating separate processes. Alternatively, spread the connections around, either by introducing a load balancer, or by varying the target options for each spawned process. See https://www.cloudera.com/documentation/enterprise/latest/topics/impala_dedicated_coordinator.html and http://www.cloudera.com/documentation/other/reference-architecture/PDF/Impala-HA-with-F5-BIG-IP.pdf for further guidance and examples on this. ... View more