anchor.diff:      ...
       "aggregations": {
           "my_buckets": {
  -            "after_key": { <1>
  +            "after_key": {
                   "date": 1494288000000,
                   "product": "mad max"
               },
  
positive.code: --------------------------------------------------
  // TESTRESPONSE[s/\.\.\.//]
  
  <1> The last composite bucket returned by the query.
  
  NOTE: The `after_key` is equals to the last bucket returned in the response before
  any filtering that could be done by <<search-aggregations-pipeline, Pipeline aggregations>>.
  If all buckets are filtered/removed by a pipeline aggregation, the `after_key` will contain
  the last bucket before filtering.
  
  The `after` parameter can be used to retrieve the composite buckets that are **after**
  the last composite buckets returned in a previous round.
  For the example below the last bucket can be found in `after_key` and the next
  round of result can be retrieved with:
  
  [source,console,id=composite-aggregation-after-example]
  --------------------------------------------------
  
negative.code: --------------------------------------------------
  
  <1> Should restrict the aggregation to buckets that sort **after** the provided values.
  
  NOTE: The `after_key` is *usually* the key to the last bucket returned in
  the response, but that isn't guaranteed. Always use the returned `after_key` instead
  of derriving it from the buckets.
  
  ==== Early termination
  
  