Question 1

What's the difference between a key-value store and a relational database (SQL)?

Accepted Answer

A key-value store retrieves data using a single unique key (like looking up a word in a dictionary). A relational database stores data in tables with rows and columns and supports complex queries (JOINs, aggregations, ad-hoc filtering). Key-value stores are usually simpler and faster for direct lookups, while SQL databases are better when you need flexible querying and relationships between many tables.

Question 2

When should I use a key-value store?

Accepted Answer

Use a key-value store when your main access pattern is "get value by key" and you need very fast reads/writes at scale. Common uses include session storage, caching (sometimes with a dedicated cache), user profiles by user ID, feature flags/config by key, shopping carts, rate limiting counters, and idempotency tokens. Avoid it when you need frequent ad-hoc queries, complex filtering, or multi-table joins.

Question 3

How much does a key-value store cost?

Accepted Answer

Cost depends on the managed service and your workload. Typical pricing factors include: storage size (GB), read/write operations or throughput (requests per second), data transfer (egress), replication/backup features, and optional features like global replication. Some services offer on-demand pricing (pay per request) or provisioned capacity (pay for reserved throughput). For self-managed options, costs include compute instances, disks, networking, and operational time.

Key-Value Store

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