Separate Database, Cache, and Object Storage Roles Across Clouds
Databases, caches, and object storage serve different roles for authoritative records, rebuildable derived data, and file assets. This interactive lesson assigns storefront orders, catalog fragments, and product images to the right layer across three clouds. Covers: Rebuildability test, cache-aside inconsistency, cache miss storms, stale reads, archive storage tiers, Amazon S3, ElastiCache, Azure Managed Redis, Memorystore. Prerequisites: Caching and storage service basics.
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An interviewer hears, “We’ll put everything in Redis for speed and fall back to S3 if needed.” That design confuses retrieval speed with data authority. For the seasonal storefront, orders and payments belong in a system of record, the durable database layer whose committed transactions define what is true. Product images belong in an asset store, where the application keeps and retrieves files. Catalog page fragments belong in a derived/performance layer, where data copied from an authoritative source can accelerate reads.
The key question is whether the data can be rebuilt from an authoritative source. A completed order cannot be reconstructed safely from a cache after a failed write, so the database must record it through durable transactional behavior. A product image is not a database row or a cache entry. It is a file stored as an object ...