The answer
The detailed design of a system. It contains database schemas, API contracts, internal logic, error cases, and edge cases. A developer should be able to code from the LLD without asking more questions.
What Is Low-Level Design (LLD)? With Example
What is low-level design (LLD)?
More FAQs in What Is Low-Level Design (LLD)? With Example
Database schemas (collections, fields, types, indexes, relationships), API contracts (endpoints, methods, request/response shapes, status codes), internal logic, error cases, and edge cases.
HLD is the big picture (components, communication, tech stack). LLD is the detail (schemas, endpoints, logic, errors). HLD settles architecture; LLD settles implementation.
Detailed enough that any developer can code from it without asking questions. Each API should have schema, contract, logic, errors, and edge cases. The point is to enable handoffs and accurate estimates.
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