Pod load distribution in Kubernetes - kubernetes

Question

I have a service in Kubernetes that receives Http requests to create users,
Only with 1 pod, it correctly reaches 100 requests per minute, after this, it has latencies, the point is that if you hold 100 requests with 1 pod, should you keep 500 requests per minute with 5 pods?
Because even with 10 pods, when exceeding 100 orders per minute, dont correctly distributed the load and appears latency in the services.
The default load configuration I understand is round robin, the problem is that I see that the ram increases only in one of the pods and does not distribute the load correctly.
This is my service yaml deploy and my HPA yaml.
Deploy Yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: create-user-service
labels:
app: create-user-service
spec:
replicas: 1
selector:
matchLabels:
app: create-user-service
template:
metadata:
labels:
app: create-user-service
spec:
volumes:
- name: key
secret:
secretName: my-secret-key
containers:
### [LISTPARTY CONTAINER]
- name: create-user-service
image: docker/user-create/create-user-service:0.0.1
volumeMounts:
- name: key
mountPath: /var/secrets/key
ports:
- containerPort: 8080
env:
- name: PORT
value: "8080"
resources:
limits:
cpu: "2.5"
memory: 6Gi
requests:
cpu: "1.5"
memory: 5Gi
livenessProbe: ## is healthy
failureThreshold: 3
httpGet:
path: /healthcheck/livenessprobe
port: 8080
scheme: HTTP
initialDelaySeconds: 30
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 5
---
apiVersion: v1
kind: Service
metadata:
name: create-user-service
spec:
ports:
- port: 8080
targetPort: 8080
protocol: TCP
name: http
selector:
app: create-user-service
type: NodePort
HPA Yaml
apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
name: create-user-service
spec:
maxReplicas: 10
minReplicas: 1
scaleTargetRef:
apiVersion: apps/v1
kind: Deployment
name: create-user-service
metrics:
- type: Resource
resource:
name: cpu
targetAverageUtilization: 75
- type: Resource
resource:
name: memory
targetAverageUtilization: 75
- external:
metricName: serviceruntime.googleapis.com|api|request_count
metricSelector:
matchLabels:
resource.type: api
resource.labels.service: create-user-service.endpoints.user-create.cloud.goog
targetAverageValue: "3"
type: External
What may be happend?.
Thank you all.