The answer
Skipping design entirely and jumping to code, leading to ad hoc architecture and rework. A close second is over-documenting instead of writing just enough to enable the next step.
HLD vs LLD: Interview Questions and Answers
What is the biggest design mistake teams make?
More FAQs in HLD vs LLD: Interview Questions and Answers
HLD is the big picture (components, communication, tech stack, data flow). LLD is the detail (schemas, API contracts, logic, errors, edge cases). HLD settles architecture; LLD settles implementation.
HLD first, then LLD. You decide architecture before detailing implementation. LLD depends on the choices made in HLD.
Database schemas with types and indexes, API contracts (endpoints, methods, request/response shapes, status codes), internal logic, error cases, and edge cases. Enough for a developer to code without questions.
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