Persist thumbnail locally
During discussions with developers from other education platforms, the following idea was brought up: we could also store the thumbnails (preview-images) in elasticsearch. Then all the data needed in the frontend would already be available locally and the user would not have to make third-party requests for each of them. This would probably have a positive impact on performance.
Edit: instead of the implementation of the elasticsearch-approach a more lightweight webserver-approach (see below in the issue-comments) seems to be the better alternative
Edited by Mirjan Hoffmann