1 min lesson
Tiering and the replay window
Use the lesson to respond to this. "Event volume doubled this month and the platform bill rose 50%. A manager asks you to cut capacity until the bill falls. What do you conclude?" Keep the answer plain.
Step 1 of 2
Tiering and the replay windowthe question that decides retention
- Hot
- Recent, frequently queried: fast storage, full fidelity, fully indexed
- Cold / archive
- Old, rarely read: cheap tier, accept slower retrieval
- Replay window
- How far back you might need to reprocess raw from scratch
- Past the window
- Drop or pre-aggregate raw: keep the rollup, shed the row-level cost
The replay window is the honest answer to "why are we still paying to store 18-month-old raw events?"
Month one costs $42,000 for 30 billion events, which is $1.40 per million. Month two costs $63,000 for 60 billion events, which is $1.05 per million. The bill rose 50% while the unit cost fell 25%, so the growth is usage, not waste. The numbers are made up to show the arithmetic and are not Cursor's.
Cost is easy to leave out. Whatever the design question, whether ingestion, modeling or observability, close with a cost angle unprompted: "and here's what this costs and the one lever I'd pull first." The posting asks for pragmatic build-vs-buy decisions, and a cost-aware close shows that judgment.
Learn more
Optional practice
Test yourself on Tiering and the replay window
QReads on a streaming-ingested bronze table have gotten painfully slow and the storage bill is climbing, even though total data volume looks reasonable. What's the most likely root cause and the first fix?