I ran

meltano config tap-mongodb list

today and noticed this at the end of the output:

Custom extras, plugin-specific options handled by Meltano:
_metadata.*.replication-key [env: TAP_MONGODB__METADATA___REPLICATION_KEY] current value: 'replication_key' (from `meltano.yml`)
_metadata.*.replication-method [env: TAP_MONGODB__METADATA___REPLICATION_METHOD] current value: 'INCREMENTAL' (from `meltano.yml`)

Does this mean I can specify the replication-key and replication-method via environment variables? If so, this is awesome - it’ll halve the number of tap configurations I have in YAML today (as we run this particular tap in both incremental and log-based replication modes).

I think the only caveat is that you either have to configure them in

meltano.yml

(as you've done) or declare them as settings, e.g.:

plugins:
  extractors:
  - name: tap-mongodb
    settings:
    - name: _metadata___replication_key
    - name: _metadata___replication_method