Delay Optimization and Reliability Verification of Cross-Domain OTA Update System Based on Kubernetes Microservices

Over-the-air (OTA) update systems are used to deliver software in real time for fields such as aviation, railway systems, and medical devices. This study builds a cloud-based OTA setup using Kubernetes and Istio to improve update speed and system stability across different types of devices. The system includes rolling updates, blue-green switching, gRPC transmission, and message queue scheduling. Tests were run on 72 terminals from vehicle, avionics, and medical settings. Results show that the average image transfer time dropped from 842 ms to 493 ms, and the failure rate was reduced from 3.6% to 0.8%. In 500 failure tests, the average time to restore service became 38.7% shorter. These results confirm that using containers and service-level routing helps shorten delays and reduce errors in OTA processes. The method can be applied in real-world embedded systems but may require extra tuning on older hardware or unstable networks.