Apache has several directives that control the number of server processes and maximum clients. The StartServers, MinimumSpareServers, and MaximumSpareServers directives determine the number of idle server processes available. The MaxClients directive sets the maximum number of simultaneous client requests. The ServerLimit directive sets the maximum value for MaxClients while MaxRequestsPerChild sets the limit per child process. The KeepAliveTimeout and MaxKeepAliveRequests control settings for HTTP persistent connections.