Glossary term
What is Shard key? Meaning for developers
In System Design
The field that decides which shard holds a row. Example: tenant_id in a SaaS app.
Learn it properly · System DesignLesson 25: Sharding: Splitting Data Across MachinesIndexes tuned, biggest server bought, replicas added — and the primary still drowns in writes. How sharding splits one dataset across machines, the four strategies, how to pick a shard key, and the hard problems it creates.In Full-Stack Questions
The field MongoDB uses to decide which shard stores a document. A poor key makes one shard too busy.
Learn it properly · Full-Stack QuestionsLesson 7: MongoDB Interview QuestionsSchema design, indexes, aggregation, transactions, replica sets, sharding and common anti-patterns.