Low-level design.
also: LLD · low level designHow each piece works inside: database schema, API contracts, classes and methods, algorithms, data structures and error handling.
the two-minute refresher
- LLD answers: how does each piece work internally?
- Typical content: tables, columns and indexes; endpoints and request/response formats; classes and method signatures; core algorithms.
- It also pins down error handling (retries, fallbacks) and in-memory structures such as cache key formats.
- In an interview it is the last 15-20 minutes, on one or two critical components.