The invention concerns API proxy based adaptive security. The invention implements adaptive security for API servers, while avoiding data bottlenecks and maintaining client experience. The invention provides methods and configurations for API security that may be employed at proxies for implementing routing decisions involving client messages received at said proxies. The invention also involves generating or collecting at proxies, log information that captures data corresponding to received client messages and responses from API servers—which log information correlates communications between clients, proxies and backend API servers, and includes data relevant for purposes generating API metrics and identifying anomalies and/or indicators of compromise. The invention yet further provides security server clusters configured for generating API metrics and/or identify anomalies or indicators of compromise—which may be used by proxies to terminate existing connections and block subsequent requests or messages from clients associated with the identified anomalies or indicators of compromise.