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// SOLID & Principles · 07

KISS

Clever, layered solutionleads toSimplest thing that works

Keep It Simple, Stupid: prefer what a newcomer can read and change.

How it fits together

KISS structureBeforeAfter«client»OrderEndpointOrderFacadePlace(order)only forwardsOrderServicePlace(order)«client»OrderEndpointOrderServicePlace(order)Validate, price, saveforwards
uses / calls
  • OrderEndpoint uses / calls OrderFacade
  • OrderFacade uses / calls OrderService (forwards)
  • OrderEndpoint uses / calls OrderService

Spot it

  • Only the author can explain how it works
  • A generic framework for one use case
  • Layers that only forward calls

It costs

Too simple for known needs means rework later; simple is not the same as naive.

In code

public sealed class OrderService(OrderStore store){    public async Task PlaceAsync(Order order, CancellationToken ct)    {        if (order.Lines.Count == 0)        {            throw new InvalidOperationException("An order needs at least one line.");        }​        order.Total = order.Lines.Sum(line => line.Price * line.Quantity);        await store.SaveAsync(order, ct);    }}​public sealed class OrderEndpoint(OrderService orders){    public Task PostOrderAsync(Order order, CancellationToken ct) => orders.PlaceAsync(order, ct);}
Go deeperThe full explanation and what to ask for · 1 min readExpand

KISS targets accidental complexity: what we add through our own choices, as opposed to the essential complexity of the problem itself.

Simple is not the same as easy or short. A clever one-liner can be harder to change than ten plain lines, and avoiding a needed abstraction is its own kind of complexity.

A practical test: can someone new to the code predict what it does and change it safely? If not, remove indirection before adding comments.

Ask for it

  • accidental complexity
  • essential complexity
  • indirection
  • cognitive load
  • readability

Simplify this module without changing behaviour: remove pass-through layers, generic abstractions with a single implementation and configuration nobody sets. Keep the tests green and justify each removal in one line.

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