I am a big fan of MongoDB and It's great for document storage but I am not really sure that it's the best engine for log storage. If data that you store is "flat" and well-defined than log storage based on engines like Clickhouse or Elasticsearch stach could be much more efficient. Also it's quite important how you reuse collected logs. Do you calculate aggregated metrics? Do you need full search ? And so on.

If logs are really simple and full text search needed than Logstash + Elasticsearch. If you need to calculate a lot of metrics and logs are not just text, but include numbers/values needed for aggregation than Clickhouse.