Patterns
A read-heavy system has far more reads than writes. In interviews, the main goal is to make the read path fast, cheap, and reliable. What it means A system is read-heavy when users read data much more often than they create or update it. Examples: * URL shortener redirects
Deep Dive Toolkit
Deep Dive Toolkit
Deep Dive Toolkit
Deep Dive Toolkit
Deep Dive Toolkit
Deep Dive Toolkit
Partitioning, or sharding, means splitting data across multiple machines. In interviews, use it when one database can no longer hold all the data or handle all the traffic. The basic idea A single database has limits. It can run out of: * storage, * CPU, * memory, * read capacity, * write capacity. Sharding solves
Deep Dive Toolkit
A Bloom filter is a memory-efficient way to answer one question: “Have we maybe seen this item before?” It is useful when you want to avoid expensive lookups for items that definitely do not exist. The simple idea A Bloom filter is a probabilistic data structure. It can answer:
Deep Dive Toolkit
Concurrency control is about one simple question: what happens when two requests try to change the same data at the same time? In interviews, this topic shows up in booking, inventory, payments, orders, auctions, and job scheduling. The problem Many systems have shared resources. Examples: * two users try to book
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.