Inverted Index — The Dict Pattern Behind Search and Data Catalogs

An inverted index maps from values to the records that contain them — the opposite of a normal lookup table. It's the core data structure behind full-text search engines, data catalog column discovery, and any system where you need to answer 'which records contain X?' efficiently. In DE interviews, it appears as a system design component and occasionally as a coding question. Real-Time Word Index from a Stream