Dated Sep 10, 2026;
last modified on Thu, 10 Sep 2026
While high level system design concerns architecture at scale (think traffic,
storage, consistency, caching, sharding, etc.), low level design deals with
classes, methods, relationships, and state transitions. For example, when
designing a ride-share system:
System design covers a matching service, a location service, a datastore, a
queue, how data flows, scaling each piece, handling load spikes, making the
system reliable, etc.
Low level design drills down to a single part of the system, e.g., design the
Trip class and the PricingCalculator interface.
Low Level Design in a Hurry | Hello Interview Low Level Design.www.hellointerview.com.
Accessed Sep 10, 2026.
DRY - Don't Repeat Yourself;
Law of Demeter (Principle of Least Knowledge);
Separation of Concerns;
YAGNI - You Aren't Gonna Need It;
KISS - Keep It Simple, Stupid;
If you find yourself adding more parameters and if-statements to an existing
abstraction, is the abstraction still apt? Why not remove the old abstraction
and re-extract a new [more apt] abstraction? Devs frequently succumb to the
sunken cost fallacy thinking that there must have been a reason that the code
was written in a certain way.
Problem Analysis. Extract key entities and responsibilities, ask a few
questions to lock down scope, and frame the problem before touching code.
Class Design. Choose the right responsibilities, shape the method
signatures, define clear ownership, and keep the boundaries clean.
Code Quality. Encapsulation, well-managed state, sensible use of composition
or inheritance, clear separation of concerns, naming, consistency, and
dependency direction.
Extensibility and Maintainability. Can the design absorb new functionality
without being rewritten? Designs should adapt easily, without anticipating every
possible future.
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