Accessing k8s pods using ingress externally (from outside k8s cluster) is better than accessing k8s pods using service within the cluster?

Hi All,
I did a Performance test where I do Writes/ Reads into/from DB (cassandra pods).
I perfrommed read/write ops on k8s pods (Cassandra) through Ingress from a external machine (outside k8s cluster). Similarly I also tried accessing same cassandra pods from another k8s pod using service with in the same k8s cluster.
Surprisingly I could see the performance (in terms of latency) was better when i accessed via ingress!
Why accessing within the cluster via service is taking more time compared to ingress ?
Please let me know why this happens !