During Cilium v1.16.0 release we introduced version 2 of the NodeMap see: 17872ef

NodeMapV2 now contains the SPI value for the given node.

To handle upgrade and downgrade gracefully the NodeMapV2 implementation performs shadow writes into the original NodeMap.

If a roll-back to v1.15.x occurs the original NodeMap contains any values which were written into NodeMapV2 during v1.16.x deployment.

The existence of both maps need only exist in v1.16.x and can be removed in preparation for v1.17.0 release.