Two functions with the same name but different letter cases causes pattern failure - Limitation of "Amazon AWS Lambda" patternSummaryLambda functions with the same name but different cases is currently unsupported. IRE uses platform GlideRecord API to do string matching. And GlideRecord Platform API itself is case-insensitive. To be noted, in our platform any List filter queries it is also case-insensitive. Therefore, it is recommended to use different names as the above is a platform behavior .