Various examples of high speed connectors and connector assemblies that use connector side plate designs and include structures for improved thermal performance are described. In one example, a connector assembly includes a housing, a side plate on one side of the housing, and a wafer assembly that includes a row of conductors and a protrusion, with the protrusion being located at one end of the row of conductors. The side plate can include an aperture, and the protrusion can be inserted into the aperture to align the row of conductors.