Time-series collections have a built-in index on time (which is really a clustered _id index on the buckets collection), but we do not display this in listIndexes, and it is confusing to users.

This ticket is intended to start a discussion about how to solve this problem, if at all.

One option we could consider:

• Report a fake index on {time: 1} in listIndexes with some flag indicating that it is built-in and the primary index, like "builtIn: true"
• Secondary indexes on {time: 1} will not have this "builtIn" flag. In this way, users can differentiate between the built-in index and any secondary indexes they build.