- Improved FormatMap: Improves performance by about 4x, or nearly 2x in the worst case ([#112661](https://github.com/kubernetes/kubernetes/pull/112661), [@aimuz](https://github.com/aimuz)) [SIG Node]
- Improved misleading message, in case of no metrics received for the `HPA` controlled pods. ([#114740](https://github.com/kubernetes/kubernetes/pull/114740), [@kushagra98](https://github.com/kushagra98))

### Other notable changes

* Kubernetes json deserializer is now case-sensitive to restore compatibility with pre-1.8 servers. ([#65157](https://github.com/kubernetes/kubernetes/pull/65157), [@caesarxuchao](https://github.com/caesarxuchao))
    * If your config files contains fields with wrong case, the config files will be now invalid.

  to avoid disruption to existing Pod and PVC objects at that time. Azure File CSI driver does not support using same persistent
  volume with different fsgroups. When CSI migration is enabled for azurefile driver, such case is not supported.
  (there is a case we support where volume is mounted with 0777 and then it readable/writable by everyone) ([#96293](https://github.com/kubernetes/kubernetes/pull/96293), [@andyzhangx](https://github.com/andyzhangx))

## Changelog since v1.9.8

### Action Required

* ACTION REQUIRED: Kubernetes JSON deserializer is now case-sensitive to restore compatibility with pre-1.8 servers. If your config files contains fields with wrong case, the config files will be now invalid. ([#65298](https://github.com/kubernetes/kubernetes/pull/65298), [@nikhita](https://github.com/nikhita))

- The scheduling queue didn't notice any extenders' failures, it could miss some cluster events,
  and it could end up Pods rejected by Extenders stuck in unschedulable pod pool in 5min in the worst-case scenario.

## Changelog since v1.8.14

### Action Required

* ACTION REQUIRED: Kubernetes JSON deserializer is now case-sensitive to restore compatibility with pre-1.8 servers. If your config files contains fields with wrong case, the config files will be now invalid. ([#65410](https://github.com/kubernetes/kubernetes/pull/65410), [@nikhita](https://github.com/nikhita))

### Other notable changes

- Promote NodeLease feature to GA.
The feature make Lease object changes an additional healthiness signal from Node. Together with that, we reduce frequency of NodeStatus updates to 5m by default in case of no changes to status itself ([#84351](https://github.com/kubernetes/kubernetes/pull/84351), [@wojtek-t](https://github.com/wojtek-t))

* kubeadm: fix an issue where 'config view' did not return a config in case of a 1.12 cluster ([#69969](https://github.com/kubernetes/kubernetes/pull/69969), [@neolit123](https://github.com/neolit123))

- Ignore the case when comparing azure tags in service annotation. ([#104705](https://github.com/kubernetes/kubernetes/pull/104705), [@nilo19](https://github.com/nilo19))
- Ignore the case when updating Azure tags. ([#104593](https://github.com/kubernetes/kubernetes/pull/104593), [@nilo19](https://github.com/nilo19))

#### Storage

- When PodInfoOnMount is enabled for a CSI driver, the new csi.storage.k8s.io/ephemeral parameter in the volume context allows a driver's NodePublishVolume implementation to determine on a case-by-case basis whether the volume is ephemeral or a normal persistent volume ([#79983](https://github.com/kubernetes/kubernetes/pull/79983), [@pohly](https://github.com/pohly))