Zalando trades 7‑year homegrown ad join for Flink, cuts cost in half
Zalando’s Ad Platform replaced a bespoke, in‑memory stream join that processed up to 200 MB/s with Apache Flink. The migration eliminated in‑memory state loss on restarts, reduced infrastructure spend by roughly 50%, and kept the 15‑minute event‑matching window intact. Unmatched events are now persisted until their counterpart arrives.