How it works
Document stores such as MongoDB and Firestore keep each record as a JSON-like document that can nest lists and objects. Key-value stores such as Redis map a key straight to a value. Wide-column and graph databases cover more specialised shapes of data.
NoSQL databases usually let each record have its own shape and are built to spread across many machines. The trade-off is that joins, strict schemas and guarantees across many records are weaker or left to the application, although most now offer transactions in some form.
Related terms
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The two families