In Kubernetes, **Quality of Service (QoS) classes** define how resources (CPU and memory) are allocated to pods, especially during times of resource contention. The three QoS classes are:

* **Guaranteed**
* **Burstable**
* **BestEffort**

Here’s a breakdown of the **difference between Burstable and Guaranteed QoS** classes:

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### ✅ **Guaranteed QoS**

* **Requirements:**

  * Pod must have **equal `requests` and `limits`** for **both CPU and memory** for **all containers**.
* **Behavior:**

  * Kubernetes treats these pods with the **highest priority**.
  * Guaranteed resources are **reserved** for the pod.
  * Least likely to be **evicted** when a node runs out of memory.
* **Use Case:** Critical workloads that must not be interrupted, such as databases or key backend services.

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### ⚡ **Burstable QoS**

* **Requirements:**

  * Pod has **both `requests` and `limits` set**, but they are **not equal**, or **only set for some containers**.
* **Behavior:**

  * Resources are **guaranteed up to the request**, but can **burst** up to the limit if resources are available.
  * Lower priority than Guaranteed but higher than BestEffort.
  * Can be **evicted** under memory pressure if higher priority pods need resources.
* **Use Case:** Non-critical apps that can scale up temporarily or tolerate being restarted.

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### Comparison Summary:

| Feature              | **Guaranteed**           | **Burstable**                               |
| -------------------- | ------------------------ | ------------------------------------------- |
| `requests == limits` | Yes (for all containers) | Not always (or partial containers)          |
| Resource Priority    | Highest                  | Medium                                      |
| Eviction Risk        | Lowest                   | Medium                                      |
| Resource Usage       | Reserved fully           | Bursts above requests if resources are free |
| Ideal for            | Critical apps            | Apps with variable demand                   |

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