# 📅 Day 22 | AWS DynamoDB — Serverless NoSQL Database in AWS ⚡☁️

Today, I learned about AWS DynamoDB, a fully managed, serverless, NoSQL database service designed to provide fast and predictable performance with seamless scalability.

DynamoDB is a key-value and document database that delivers single-digit millisecond performance at any scale. It’s a favorite for DevOps and Cloud Engineers because it removes the administrative burden of operating and scaling distributed databases.

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⚡ AWS DynamoDB – DevOps Explanation

What is AWS DynamoDB?

AWS DynamoDB is a Serverless NoSQL Database that allows you to store and retrieve any amount of data and serve any level of request traffic.

Unlike relational databases (RDS), DynamoDB is non-relational, meaning it doesn’t use fixed schemas or complex joins. AWS handles the:

• Hardware provisioning
• Setup and configuration
• Replication and software patching
• Cluster scaling

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Why DevOps Engineers Use DynamoDB

DynamoDB is the go-to choice when:

• You need extreme scale (millions of requests per second)
• You require consistent low latency (single-digit milliseconds)
• You want a serverless architecture (no instances to manage)
• You need global availability (Global Tables)

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Core Concepts (The Fundamentals)

• Tables: Similar to a table in SQL, but with no fixed schema.

• Items: Similar to a "row." Each item is a collection of attributes.

• Attributes: Similar to a "column." Can be strings, numbers, binaries, or even JSON (Maps/Lists).

• Primary Key: Must be defined at creation. It consists of:

• Partition Key (PK): Used for internal data distribution.

• Sort Key (SK): (Optional) Used to sort data within a partition.

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DynamoDB Features & Architecture

• High Availability: Data is automatically replicated across three Availability Zones (AZs) within a region.

• Read Consistency: * Eventually Consistent (Default) – Best performance, lowest cost.

• Strongly Consistent – Returns the most up-to-date data.

• DynamoDB Streams: Captures item-level changes (Insert/Update/Delete) and triggers AWS Lambda—perfect for event-driven apps.

• TTL (Time to Live): Automatically deletes expired items to reduce storage costs.

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Capacity Modes (How you pay)

1. On-Demand: You pay per request. Best for unpredictable workloads or new apps.
2. Provisioned: You specify RCU (Read Capacity Units) and WCU (Write Capacity Units). Best for predictable traffic and cost control (supports Auto Scaling).

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Indexing for Performance

Since you can only query by Primary Key, you use Indexes to query other attributes:

• Local Secondary Index (LSI): Same Partition Key, different Sort Key. (Must be created with the table).
• Global Secondary Index (GSI): Different Partition Key AND different Sort Key. (Can be created anytime).

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Security in DynamoDB

• IAM: Control who can read/write to specific tables.
• Encryption at Rest: All data is encrypted by default using AWS KMS.
• VPC Endpoints: Keep traffic within the AWS network (Gateway Endpoint).
• Fine-Grained Access Control: Using IAM policies to restrict access to specific items or attributes.

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Common Use Cases

• Serverless Apps: Paired with AWS Lambda and API Gateway.
• Session Management: Storing user sessions for web applications.
• Gaming: Storing leaderboards and player profiles.
• IoT: Ingesting massive amounts of sensor data.

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Advantages

• No Servers to Manage: Zero operational overhead.
• Auto-Scaling: Grows and shrinks based on traffic.
• Enterprise Grade: Supports ACID transactions and 99.999% availability with Global Tables.
• Performance at Scale: Latency does not increase as the database grows.

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Limitations

• No Joins: You must model data to avoid needing joins.
• Query Limitations: You cannot perform complex SQL-like queries easily.
• Item Size: Maximum size per item is 400 KB.

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Interview One-Line Answer

AWS DynamoDB is a fully managed, serverless NoSQL database that provides consistent, single-digit millisecond latency at any scale. It supports both document and key-value data models, offers built-in security, backup/restore, and multi-region replication via Global Tables.

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Thank You

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