Postgres with upserts (and triggers if your de-duplication logic can't be handled on the backend)?

OLAP works here, but is not great depending on how fast you need info to be available. If you're generating reports, Postgres is fine as long as your queries are properly optimized, and you can get them within minutes for massive workloads. If you need near-instant (sub 1s) results, I would recommend you sync your RDBMS to a columnar database like ClickHouse, and let the better data layout work in your favor, rather than trying to constrain a row-based DB to act like it's not.

Otherwise, both are rock solid and simple to use. I've dealt with more intensive workloads than you mentioned, with the same use-case and Postgres worked very well. ClickHouse never had a problem.