Databases are the heart of most systems. They’re where your precious data lives, and choosing the right database—and designing it properly—can make or break your system’s performance and reliability.
But here’s the thing: there’s no one-size-fits-all database solution. SQL or NoSQL? Relational or document-based? Strong consistency or eventual consistency? The answer is always: “It depends.”
What You’ll Learn
In this section, we’ll explore everything you need to know about databases for system design interviews:
- SQL vs NoSQL: Understanding when to use each and why
- Database scaling: Vertical vs horizontal scaling strategies
- Replication: Keeping multiple copies of your data for reliability and performance
- Sharding: Partitioning data across multiple databases
- Indexing: Speeding up queries without loading everything into memory
- ACID properties: Understanding transactions and consistency
- CAP theorem: The fundamental trade-off in distributed databases
- Database types: From relational databases to key-value stores, document databases, and graph databases
Why Databases Matter
Almost every system design interview will involve database decisions. Whether you’re designing Twitter, YouTube, or an e-commerce platform, you’ll need to:
- Choose the right type of database for your use case
- Design a schema that supports your queries efficiently
- Plan for scale from thousands to millions of users
- Ensure data isn’t lost even when things go wrong
- Balance consistency, availability, and performance
Real-World Patterns
We’ll look at how real companies solve database challenges:
- How Netflix handles millions of concurrent streams
- How Facebook stores billions of social connections
- How Amazon ensures you never lose items in your shopping basket
- How banking systems maintain strict consistency whilst staying performant
Ready to become a database design expert? Let’s dive in!