CREATE TABLE default.events (
      `timestamp` DateTime
      `event` String -- e.g. 'product.updated' or empty/null
      `message` -- human readable message
      `raw` -- the raw message - this is very useful when pushing logs that aren't JSON - you just let the `event` be null and dump the entire message here
    )
    ENGINE = MergeTree
    PARTITION BY toDate(timestamp)
    ORDER BY (timestamp, event)
    TTL timestamp + toIntervalMonth(6)

Of course, the more columns you splat out (e.g. like correlation_id, user_id, order_id, etc) the better you can index and expect those queries to perform but in general I don't bother outside the obvious core domain ones (exampled above), the performance is so good that unindexed queries are significantly faster than indexed queries in Loki. I have reached the point where I JSON extract on-the-fly for the WHERE clause with very large queries with no meaningful performance issues.