Surrogate keys are about setting expectations on cache purging.
Presently we use a combination of all parameters to set changing surrogate keys depending on the result of the `ArticleApiIndexService`. This approach has two limitations:
- if two set of params lead to the same exact set of articles, we still create two different caches
- deleted articles will remain for 24 hours in the cache because the cache key doesn't take the record keys into account
By simply using record keys we make sure that different params leading to the same result set will share the same cache and that deleted keys won't appear anymore in the cache.
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