Affinity:

spec.affinity
spec.affinity.nodeAffinity
spec.affinity.podAntiAffinity

   spec:
     affinity:
       nodeAffinity:
         requiredDuringSchedulingIgnoredDuringExecution:
           nodeSelectorTerms:
           - matchExpressions:
             - key: node_group
               operator: In
               values:
               - arm_db
             - key: topology.kubernetes.io/zone
               operator: In
               values:
               - us-east-1a

 affinity:
   podAntiAffinity:
     requiredDuringSchedulingIgnoredDuringExecution:
       - labelSelector:
           matchExpressions:
             - key: app
               operator: In
               values:
                 - YOURAPPNAME
         topologyKey: "kubernetes.io/hostname"

• Kubernetes pod affinity and anti affinity
• 0/2 nodes are available: 1 Too many pods, 1 nodes(s) didn't match Pod's node affinity/selector

See also

• Kubernetes pod affinity and anti affinity, Kubernetes Node Affinity, default-scheduler, affinity:, NodeAffinity, spec.affinity.podAntiAffinity