While I was not able to find a easy to understand and implement solution, I decided to use below approach that is simple and appropriate for my use case (that's pretty complicated), I will try to present simpler example bellow:

  * let's assume our use case implies a temperature reading sensor, a couchDB import script and a map function
  * each m minutes (more or less - it should not matter) info is read from server and saved into couchDB
  * each doc should have a metaData with two values: {validityStart: <timestamp>, validityEnd: <timestamp>)
  * there are two kinds of DOCs:
    * current doc, using sensorId as key and {validityStart: <timestamp>, validityEnd: 0)
    * archived doc, using uuid as key and {validityStart: <timestamp>, validityEnd: <timestamp>)
  * each time a reading is done, 
    * if existing reading already existing for this sensor:
      * create new archived doc from current doc + updated validityEnd timestamp
    * update/create current doc with new validityStart timestamp and new temperature