Should I update HLD and LLD during coding?
Yes. Designs evolve. When you find edge cases during coding, add them to the LLD. When the architecture changes, update the HLD. The doc is alive.
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More FAQs in How to Write a Good HLD and LLD Document
Start with the goal in one sentence. Use an architecture diagram. Label components, communication, and protocols. Keep it short. Skip the fluff about why popular tools are popular.
Use tables for schemas. Show API contracts with method, path, body, response, and status codes. Write logic as numbered steps. List error cases explicitly. Include edge cases. The goal is a developer can code from it without questions.
As short as possible while being clear. HLD often fits on one page with a diagram. LLD is longer because it covers every endpoint, but each section should be just the necessary detail.
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