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Key-Value Database

Key-value database (ya key-value store) ek NoSQL database hai jo data ko simple key-value pairs me…

Overview

Key-Value Database — Quick Facts

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Property: Detail

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Full Name: Key-Value Database (Key-Value…

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Category: NoSQL Database / Data Store

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Data Model: Key-Value Pairs

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Infobox

📊 | Property | Detail | |---|---| | Full Name | Key-Value Database (Key-Value Store) | |…

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Key-Value Database Kya Hai

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Key: Ek unique string jo…

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Value: Key ke saath stored data —…

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Complex queries (SQL WHERE, JOIN,…

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Schema enforcement (columns/tables…

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Kyun Use Karte Hain

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In-memory KV stores (Redis,…

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Database query jo 50ms leti hai,…

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Real-time applications jahan har…

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Agar data access pattern sirf "get…

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Data Model

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Must be unique within the…

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Usually string type (some systems…

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Length limits vary by…

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Naming conventions important (more…

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Core Operations

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INCR/DECR: Counter atomically…

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SETNX: Set only if not exists…

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CAS (Compare-And-Swap):…

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In-Memory vs On-Disk

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Data primarily RAM me stored hota…

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Fastest possible access:…

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Volatile: Server restart hone pe…

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Examples: Redis, Memcached,…

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Popular Key-Value Databases Comparison

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Redis — Deep Dive

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In-memory with optional…

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Rich data structures: Strings,…

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Atomic operations: INCR, LPUSH,…

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Pub/Sub messaging built-in

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Memcached

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Pure in-memory — no disk…

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Simple protocol: GET, SET, DELETE,…

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Value type: Opaque bytes only (no…

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Multi-threaded architecture…

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Amazon DynamoDB

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Serverless — no provisioning,…

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Single-digit millisecond latency…

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Built-in replication (3 AZs within…

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Global Tables for multi-region…

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etcd

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Written in Go

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Raft consensus algorithm for…

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Strong consistency (linearizable…

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Watch API: key changes pe…

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RocksDB

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Writes go to in-memory buffer…

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When MemTable full → flush to disk…

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Background compaction merges SST…

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Reads: Check MemTable first → then…

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Riak aur Aerospike

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Distributed key-value store…

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Eventually consistent (tunable…

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CRDTs (Conflict-free Replicated…

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No single point of failure…

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Caching Use Case

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LRU (Least Recently Used): Sabse…

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LFU (Least Frequently Used): Sabse…

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TTL-based: Time expire hone pe…

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Random: Random eviction (simplest,…

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Session Management

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Sub-millisecond session lookup

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TTL-based auto-expiration (session…

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Shared session store across…

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Scale independently from…

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Configuration aur Feature Flags

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Key: config:{app}:{setting} (e.g.,…

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Value: Configuration value

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Watch/subscribe for real-time…

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Key: feature:{flag_name} (e.g.,…

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Rate Limiting aur Counters

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Key: ratelimit:{resource}:{window}…

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Value: Request count

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INCR operation pe har request pe…

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TTL = window duration (e.g., 60…

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Leaderboards aur Real-Time Rankings

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ZADD: Player add karo with score…

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ZRANGE / ZREVRANGE: Top N players…

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ZRANK / ZREVRANK: Player ki ranking

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ZINCRBY: Score increment karo

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Message Queues aur Pub/Sub

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Publisher: PUBLISH channel:news…

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Subscriber: SUBSCRIBE channel:news…

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Fire-and-forget: Agar subscriber…

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Use: Real-time notifications, live…

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Distributed Key-Value Stores

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Single server ki RAM/storage limit…

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High availability — ek node fail…

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Geographic distribution — users ke…

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Client-side sharding: Client…

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Partitioning aur Sharding

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Key ka hash calculate karo → hash…

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Even distribution of data across…

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Problem: Nodes add/remove karne pe…

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Virtual ring pe nodes aur keys…

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Replication aur Consistency

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Asynchronous by default (master…

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WAIT command for synchronous…

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Replica can serve reads (read…

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Automatic failover with…

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CAP Theorem aur Key-Value Stores

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C (Consistency): Sab nodes pe same…

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A (Availability): Har request ko…

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P (Partition Tolerance): System…

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Persistence Models

🌐 In-memory key-value stores me persistence kaise achieve hota hai: Redis Persistence…

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Key-Value vs Other Database Types

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Key Design Patterns

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Use colon (:) as separator:…

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Examples: user:1001:profile,…

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Short but descriptive

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Consistent across application

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Security Considerations

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Redis: requirepass directive ya…

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DynamoDB: IAM-based authentication

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etcd: Client certificates (mTLS)

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Never expose KV store directly to…

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Performance Tuning

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Pipeline commands: Multiple…

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Connection pooling: Maintain…

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Appropriate data structures: Hash…

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Avoid KEYS command in production…

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Mermaid Diagram

🔍 `mermaid flowchart TB subgraph Application["Application Layer"] A1["Web Server / API"]…

Comparison

In-Memory vs On-Disk

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Latency: Microseconds

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Durability: Volatile (default)

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Data Size: Limited by RAM

Comparison

Popular Key-Value Databases Comparison

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Redis: Server

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Memcached: Server

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DynamoDB: Managed Cloud

Comparison

Key-Value vs Other Database Types

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Data Model: Key → Value

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Query: GET/PUT by key

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Schema: Schema-free

Diagram

Visual Flow

📊 Diagram visualization — details in narration

Quiz — Question 1

Key-Value Database ka sabse sahi definition kya hai?

Quick Quiz

Quiz — Question 2

Key-Value Database ka 'Full Name' kya hai?

Complete! 🎉

Key-Value Database Complete!

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Key-Value Database Complete

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