# Graceful degradation

> When a system cannot do everything, switch off the costly features first, so the core of the product keeps working.

Graceful degradation drops optional work on purpose when the system is under stress, so users keep the part that matters.

## Use it when

- Some features cost far more than they earn, such as recommendations, exports or reports.
- A spike or a failing dependency threatens the whole page.
- You can show something useful without the feature, like a default or a cached copy.

## How it works

Each feature gets a rank, and under pressure the system turns off the highest-cost, lowest-need ones first. A shop page can render without the recommendation panel, so when the recommender is slow, the page skips it after a short deadline. Netflix shows a generic row when personalization is down. The user sees less, not nothing.

## What it costs

Someone has to decide which features may go, and that is a product call, not an engineering one. Degraded paths need testing, because a path that has never run tends to fail the first time it matters. A degraded system can also look healthy while it quietly loses value, so count how often it runs.

## In Quorum



**Drop dearest** sits under **Overload** on an App Server. Past its load line, the App Server drops the request kinds that cost the most CPU first, so the cheap kinds keep their latency. Against [Load shedding](https://wiki.playquorum.dev/patterns/load-shedding.md), which drops the lowest-value kinds, this keeps more of the Users happy when the expensive kinds are the cause. Check both captions: the Apdex is higher here and the errors fall, though the dropped kinds still count as errors. If a Node has both, it degrades first. [Graceful degradation](https://wiki.playquorum.dev/research/graceful-degradation.md) needs [Feature flags](https://wiki.playquorum.dev/research/feature-flags.md). The glossary defines [graceful degradation](https://wiki.playquorum.dev/glossary/graceful-degradation.md).

Source: https://wiki.playquorum.dev/patterns/graceful-degradation