Performing aggregation operations in MongoDB to sort data based on specific properties

Question

I want to sort the data in MongoDB using aggregation operations based on specific attributes. For example, I have hundreds of records like this (under the 'specs' array with spec_id: 1, code: ram, value: 6), and this pattern continues for many phone brands. Additionally, each phone has various spec_id values under the 'specs' array. What I'm looking to achieve is to list the values each spec_id takes under a corresponding 'code' as an array. If a value appears multiple times (e.g., 6 occurs in multiple entries), it should only be listed once, with a 'count' indicating how many times it appears. In the end, I'd like the output to be structured like this within the 'group_by_ram' array: inside the 'buckets' array, there should be objects with 'key' representing the unique values and 'doc_count' indicating how many times each value appears. I attempted to do this using $facet, but since I also used $unwind and $unwind isn't the most reliable option, I'm seeking an alternative solution.