Database services

Foundational notes for AWS Certified Cloud Practitioner (CLF-C02). Read them in order the first time through, then use them as a revision sweep before you book.

12 study points. Everything here is exam-oriented: each point is a fact or a distinction that CLF-C02 items are built on. Test yourself against the practice exam once you can explain a section without re-reading it.

Database

Amazon RDS (Relational Database Service) is a managed service for running traditional SQL databases in the cloud. It supports several popular engines: Amazon Aurora, MySQL, PostgreSQL, MariaDB, Oracle, and Microsoft SQL Server. RDS handles the heavy lifting of database administration, including backups, patching, and scaling, so you can focus on your application logic. When you need a structured, relational database with tables, rows, and SQL queries, RDS is almost always the right starting point.

RDS Read Replicas let you create read-only copies of your database to offload read traffic from the primary instance. They are available for MySQL, Aurora, Oracle, and PostgreSQL engines. For example, if your application has a dashboard that runs complex reporting queries, you can point those queries at a read replica so they don’t slow down your production database. Read replicas can also be created in different Regions for disaster recovery or to serve users closer to their geographic location.

Amazon DynamoDB is AWS’s fully managed NoSQL database, designed for applications that need single-digit millisecond latency at any scale. Unlike RDS, DynamoDB does not use tables with rigid schemas; instead, it stores data as key-value pairs or documents. It scales automatically, so you never have to worry about provisioning capacity. DynamoDB is the only NoSQL database engine offered as a managed service on AWS, and it’s ideal for use cases like gaming leaderboards, IoT data, and shopping carts.

Amazon ElastiCache is a fully managed in-memory data store that dramatically boosts the performance of your applications. It supports two engines: Redis and Memcached. Instead of querying your database every time a user requests the same data, your application can first check ElastiCache. If the data is already cached in memory, it’s returned in microseconds rather than milliseconds. For example, an e-commerce site can cache product catalog data in ElastiCache so that browsing feels instantaneous.

Amazon Redshift is a fully managed data warehouse service designed for analyzing large volumes of structured data using SQL. It’s optimized for running complex analytical queries across petabytes of data, making it ideal for business intelligence and reporting. Redshift is not meant for transactional workloads like an online store; it’s for answering questions like “What were our total sales by region over the last three years?” It offers high availability and elastic resizing to match your analytical needs.

AWS Database Migration Service (DMS) helps you migrate databases to AWS quickly and securely. The source database remains fully operational during the migration, minimizing downtime for applications that depend on it. DMS supports homogeneous migrations (like Oracle to Oracle) and heterogeneous migrations (like Oracle to Aurora) when combined with the AWS Schema Conversion Tool. For example, a company moving from an on-premises MySQL database to Amazon Aurora can use DMS to replicate the data with near-zero downtime.

Multi-AZ deployment is an RDS feature that provides high availability and failover support. When you enable Multi-AZ, AWS creates a standby replica of your database in a different Availability Zone and synchronously replicates all transactions to it. If the primary instance fails, RDS automatically fails over to the standby, typically within 60-120 seconds. The standby must be in a private subnet for security. This is a disaster recovery feature, not a performance feature; for read scaling, use Read Replicas instead.

EBS (Elastic Block Store) volumes are designed for reliability through automatic replication within the same Availability Zone. This means your data is protected against the failure of a single hard drive, but not against the failure of an entire AZ. For cross-AZ protection, you should take regular EBS snapshots, which are stored in Amazon S3 and can be used to recreate volumes in any AZ. This layered approach gives you both local durability and regional disaster recovery.

Amazon Aurora is AWS’s cloud-native relational database, compatible with both MySQL and PostgreSQL. It offers up to five times the throughput of standard MySQL and three times the throughput of standard PostgreSQL, with a fraction of the cost of commercial databases. Aurora automatically replicates your data across three Availability Zones with six copies of your data, making it exceptionally durable. It’s the recommended choice when you need a high-performance relational database on AWS.

Amazon Neptune is a fully managed graph database service designed for applications that work with highly connected data. It supports both the Property Graph model and the W3C RDF standard. Use cases include social networking, recommendation engines, fraud detection, and knowledge graphs. For example, if you need to find the shortest connection path between two people in a social network, a graph database like Neptune is far more efficient than a relational database.

Amazon DocumentDB is a fully managed document database service that is compatible with MongoDB workloads. It stores data as JSON-like documents, making it a natural fit for content management systems, catalogs, and user profiles where each record can have a different structure. If you’re already running MongoDB and want a managed service on AWS, DocumentDB lets you use your existing MongoDB drivers and tools without modification.

Choosing the right database service on AWS depends entirely on your use case. For structured data with relationships, use RDS or Aurora. For key-value or document data at massive scale, use DynamoDB. For caching, use ElastiCache. For analytics and reporting, use Redshift. For graph data, use Neptune. AWS provides purpose-built databases so that each workload can use the engine that fits it best, rather than forcing everything into a single general-purpose database.

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Where to go next

• Back to the AWS Cloud Practitioner overview.
• Look up any service you could not name in the AWS services glossary.
• Sit the 80-item practice exam once two or three note pages are solid.