Two scenarios can apply
1) In one of our use case, we implemented a workflow that will trigger when an asset is modified to Invalidate CDN cache
public void execute(final WorkItem workItem, final WorkflowSession workflowSession, final MetaDataMap arg)
throws WorkflowException {
try {
Asset asset = getAssetFromPayload(workItem, workflowSession.adaptTo(Session.class));
ResourceResolver resourceResolver = resourceResolverFactory.getServiceResourceResolver(
Collections.singletonMap("sling.service.subservice", (Object)EAEM_CACHE_INVALIDATION_PROCESS));
CdnCacheInvalidationParam cacheInvalidationParam = getCdnCacheInvalidationParam(config, asset);
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2) Did you check the AdaptiveImageServlet --> requestLastModifiedSuffix = getRequestLastModifiedSuffix(suffix);
https://github.com/adobe/aem-core-wcm-components/blob/master/bundles/core/src/main/java/com/adobe/cq...