Added content for KV database (#7295)

* Update key-value-database@l2aXyO3STnhbFjvUXPpm2.md

Added content for KV database

* Update src/data/roadmaps/redis/content/key-value-database@l2aXyO3STnhbFjvUXPpm2.md

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Co-authored-by: dsh <daniel.s.holdsworth@gmail.com>

src/data/roadmaps/redis/content/key-value-database@l2aXyO3STnhbFjvUXPpm2.md

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-# Key-value Database
+# Key-value Database
+
+Key-value Database is a non-relational (NoSQL) database that stores data as a collection of key-value pairs. In this model, each piece of data is associated with a unique identifier (key) that is used to retrieve the corresponding value. This simple structure allows for high performance and scalability, making key-value databases ideal for certain use cases. 
+
+Visit the following resources to learn more:
+
+- [@official@What is a Key-Value Database?](https://redis.io/nosql/key-value-databases/)
+- [@video@Key Value Store - System Design Interview Basics](https://www.youtube.com/watch?v=ozJHmm05EXM)