Storage Tiering
Moving data between access tiers as it cools, so rarely-read data is not paying hot-storage prices.
Object storage prices span more than an order of magnitude between standard and archive tiers, and most data is read heavily for days and then almost never. A lifecycle policy that transitions objects after 30 days and archives after 90 typically removes a large fraction of a storage bill for no engineering effort.
The costs to check before writing the policy: retrieval from archive tiers costs money and time (minutes to hours), there are minimum storage durations that make early deletion chargeable, and per-object transition requests cost money — so archiving fifty million tiny objects can cost more than leaving them.
The same idea applies to databases and logs: partition by date and move cold partitions out, and set log retention deliberately rather than accepting a default of forever.