Discussion on: Bitmasks: A very esoteric (and impractical) way of managing booleans

I absolutely love working with bitmasks! They pair incredibly well with MongoDB: there are query expressions for $bitsAllSet/$bitsAnySet + $bitsAllClear/$bitsAnyClear to make for some very succinct and expressive queries, and then there also $bit update operators for setting/unsetting bits. Field selection is a lot more straightforward; it indexes well, especially w/ compound indexes; and it just feels clean. I've found that a lot of queries are just much easier to express like this, for instance:

let cursor = Users.find({
  status: {
    $bitsAllSet: VERIFIED | FEATURED,
    $bitsAllClear: BANNED | DISABLED | PROVISIONAL
  }
}).lean().cursor();

Also, there are a lot of times in which logical expressions are much cleaner with bitmasks. For instance, say you wanted to update a doc and wanted to trigger some behavior based off of the changes; the optimal way to do this IMO is to use a findOneAndUpdate with bitwise updates ($bit) and then to return the old doc / sync the bitwise updates and to compute the XOR. Once you have the XOR of the update, it's really easy to derive events: IE status & XOR & VERIFIED -> they are verified & they weren't verified before this update. The most powerful use case I've found is for shared documents, where you have a subdocument array for user data w/ an ObjectID ref + a bitmask, and then you can use $elemMatch updates to set each users respective flags, and then you can do awesome things like taking the AND of each users flags + the XOR of an update as to derive events based of when flags are mutually set by both users and became such as a result of this update. This very simple design pattern works for a staggering number of use cases.