Core interview topics across tech roles: Networking basics: TCP, UDP, DNS, routing, subnets. Linux internals and command-line proficiency. Cloud fundamentals: AWS, IAM, VPC, scaling patterns. Containers and Kubernetes concepts. Security principles: least privilege, encryption, threat modeling. CI/CD pipelines and automation. Databases: indexing, transactions, query optimization. System design: load balancing, caching, HA. Logging, metrics, observability stacks. Incident response and troubleshooting methodology.