The essential components used in most system design interviews, explained for practical interview use.
Core Building Blocks
Elasticsearch is used when a normal database is not good enough for search. In interviews, use it for full-text search, filtering, ranking, autocomplete, and geo search. What Elasticsearch does Elasticsearch is a search engine. It helps you search through large amounts of text and structured data quickly. Examples: * search
Core Building Blocks
An API Gateway is the front door of a backend system. It gives clients one entry point and handles common tasks like routing, authentication, rate limiting, and request shaping. What an API Gateway does In a simple system, the client may call one backend service directly. Client → Backend Service In
Core Building Blocks
Blob storage is used for large files such as images, videos, PDFs, logs, and backups. In interviews, the most common pattern is simple: store metadata in the database, and store the actual file in object storage. What blob storage is Blob storage, also called object storage, stores unstructured binary data.
Core Building Blocks
A message queue helps you move slow or unreliable work out of the main request path. In interviews, it is one of the clearest ways to improve latency, reliability, and system flexibility. What a message queue does A message queue lets one service send a task or event to another
Core Building Blocks
A CDN helps users download content from servers close to them. In interviews, CDN is usually the right tool for static files, images, videos, and other content that can be cached at the edge. What a CDN does CDN means Content Delivery Network. It is a network of edge servers
Core Building Blocks
A cache is a fast storage layer used to reduce latency and database load. In system design interviews, cache is one of the most common tools, but you should only use it when the read pattern makes sense. What a cache does A cache stores frequently accessed data in memory.
Core Building Blocks
Your job is not to name a database randomly. Your job is to explain what data you need to store, how you will query it, and what consistency you need. What a database does A database stores the main business data of your system. Examples: * users * orders * payments * posts * messages