Individual skill

system-and-data-design

Decide whether the system will hold, and where the data lives: requirements and load first, then back-of-the-envelope numbers, building blocks (cache, queue, load balancer, CDN), and the data layer in depth — storage engines, indexes, replication, partitioning, transactions and consistency, batch vs stream. Use when sizing or scaling anything; choosing a database, cache, queue or index; when asked "will this hold", "how many machines", "which database", "do we need a queue", "read replica", "sharding", "eventual consistency", "why is this query slow at scale"; when designing an ingestion or processing pipeline; or when a service is slow under load rather than wrong. Do NOT use for module layout, dependency direction or domain boundaries (use architecture-first), for function- and naming-level quality (use code-complexity), for restructuring code that is already too large (use refactoring-safely), or for a low-traffic internal tool where the honest answer is one process and one database.

skills/development/system-and-data-design/SKILL.md

Source commit 849719987d9c0d6ed973bdbce8ed37b266d3b1f3

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Yes

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Observed behavior

Network or broad shell

Last checked

Nov 7, 2026

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