**[Alexander Riss](https://jira.spring.io/secure/ViewProfile.jspa?name=ariss@adobe.com)** opened **[SPR-15553](https://jira.spring.io/browse/SPR-15553?redirect=false)** and commented the messenging classes use the keySet for iterating the entrySet and cause more map lookups than needed (e.g. for headers) --- **Affects:** 4.3.8, 5.0 RC1 **Referenced from:** pull request https://github.com/spring-projects/spring-framework/pull/1394, and commits https://github.com/spring-projects/spring-framework/commit/fa09cd3737680fa1a1a35548baf7b5228b984720, https://github.com/spring-projects/spring-framework/commit/9e3f4ccce95b76e5c43a07a226871e0c5f7612d4, https://github.com/spring-projects/spring-framework/commit/e49a5d8424a0bbf059fe7fa23b13c50d39b36a7b
