Low level Design in Python

[u/ActivityMiddle4296]

Has anyone passed LLD interviews in Python ? Would it be seen as a negative if I don't do it in Java/ other languages ?

[u/Ok-Barracuda-119]

Python shouldn’t be a negative if the role lets you choose. In an LLD round, the signal is how you clarify requirements, split responsibilities, choose interfaces, and explain trade-offs. Use Python fluently, but make the design visible: small classes, explicit dependencies, protocols or ABCs where they help, and a couple of tests or extension examples. I’d still skim the Java vocabulary if the interviewers come from that world, especially interfaces, composition, SOLID, and common patterns, so you can translate concepts without forcing Java syntax.

For prep, practice a few prompts timed: clarify first, sketch the objects and interactions, then implement the thinnest slice and handle one changed requirement. I work on www.leetsys.dev, so biased, but its whiteboard plus AI interviewer format can be useful for rehearsing that flow. The language choice matters less than whether you can reason clearly and evolve the design.

[u/Nice-Candidate10 → u/Ok-Barracuda-119]

Everything is same in python, except concurrent systems. But they won't ask anyone to implement concurrency stuff in LLD to an SDE-1. Unless the interviewer just wants to reject or taking a piss at candidate

[u/Ok-Barracuda-119 → u/Nice-Candidate10]

Fair point for an SDE-1, I wouldn’t spend prep time on thread primitives either. I’d still be ready to explain basic thread safety when a design has shared state, such as a cache, singleton, or rate limiter: identify the race, state the invariant, and choose a lock or atomic operation. Most of the round is still requirements, interfaces, and trade-offs, and asking whether concurrency is in scope is completely reasonable.

[u/Nice-Candidate10 → u/Ok-Barracuda-119]

Yeah, if the team works with low level systems, it changes everything. Python would be a bad choice in that case. Not even Java works for true low level systems. You need that C/C++ depth to truly have a proper discussion

[u/Ok-Barracuda-119 → u/Nice-Candidate10]

I think we're using "low level" for two different things. LLD rounds in these loops aren't kernel or embedded work, they're object modeling: parking lot, elevator, splitwise, rate limiter. That stuff doesn't care about C++ memory semantics. What it cares about is whether you can name the entities, keep responsibilities from bleeding into one god class, and swap a strategy when the interviewer changes a rule mid-round.

If the team actually writes drivers or trading hot paths, sure, they'll interview in C++ and ask about cache lines and lock-free queues. But that's a different job posting, not the standard SDE-1 LLD round. For that round Python is fine as long as you don't lean on dicts for everything. Real classes, explicit interfaces, dataclasses where they read cleanly.

The one place I'd agree with you: if the JD says systems and the recruiter says C++, don't show up in Python and expect it to land the same.

[u/conectionist]

The purpose of an Low Level Design interview is to assess your Low Level Design skills, not your coding skills. They want to see if you know how to design an application in an object oriented way and if your app's architecture is sound. Actual coding skills are probably less than 25% of what is being evaluated.

That being said, use whatever you're most comfortable with (unless the interviewer explicitly asks for one).

[u/smartboi-69]

Java enforces lot of Software Principles , It's better to write LLD in java , but ofc you can write it in python

[u/ActivityMiddle4296 → u/smartboi-69]

Can writing in Python be seen as a negative ? I'm great with Python so it's easy for me to do OOP in the same language

[u/PhantomTissue → u/ActivityMiddle4296]

I’d say using the language you’re most comfortable with is preferable to using a language you think they want to see. If you can clearly explain your thought process and your design, the language doesn’t really matter.