## Problem Design a build system that compiles targets in dependency order, using cached results where possible. Each target has a list of source files and dependencies on other targets. A target needs rebuilding if any source file or dependency has changed since the last build. ```python class BuildSystem: def add_target( self, name: str, sources: list[str], deps: list[str], build_fn: callable ) -> None: def build(self, target: str) -> str: # returns build artifact path def invalidate(self, source_file: str) -> None: # mark file as changed ``` ## Example ``` build.add_target("libfoo", sources=["foo.c"], deps=[], build_fn=compile_c) build.add_target("app", sources=["main.c"], deps=["libfoo"], build_fn=link) build.build("app") # compiles libfoo, then app build.build("app") # fully cached: nothing recompiles build.invalidate("foo.c") build.build("app") # recompiles libfoo AND app (transitive invalidation) ``` ## Follow-ups 1. How do you detect circular dependencies? 2. Which targets can be built in parallel? How do you schedule them? 3. How would you implement content-based caching (hash of inputs) vs. timestamp-based?

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Build Architect: Design a Dependency-Aware Build System

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Problem Design a build system that compiles targets in dependency order, using cached results where possible. Each target has a list of source files and dependencies on other targets. A target needs rebuilding if any source file or dependency has changed since the last build. Example Follow-ups How do you detect circular dependencies? Which targets can be built in parallel? How do you schedule them? How would you implement content-based caching (hash of inputs) vs. timestamp-based?

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It covers the following topics: System Design, Coding, Phone, Onsite .

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Build Architect: Design a Dependency-Aware Build System

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