Ranked in these QuestionsQuestion Ranking
Pro Ability to run ad-hoc SQL like queries on realtime big data
Couchbase N1QL allows native SQL processing over JSON data with high performance indexing for low latency queries at scale.
Pro Open source
Couchbase and Couchbase Mobile are open source and released under the Apache License.
Pro Ability to make predefined fast queries
With Couchbase you can make "Views" of data, which are practically predefined queries which are fetched with an O(1) algorithm.
Con No model mapper for Android
Couchbase does not have a model mapper for Android built-in and out of the box, instead you will have to write your own from scratch.