Explained: AWS ENIs (Elastic Network Interfaces)

Your production database server starts throwing errors at 2 a.m. The on-call engineer spins up a replacement instance, and now the scramble begins: update the DNS record, wait for the TTL to expire, reconfigure the firewall rules that were pinned to the old private IP, and hope every downstream service notices the change. Twenty minutes of downtime, most of it spent chasing a network identity that was welded to a machine that no longer exists. Th… Read More

Architecture: AWS Fargate

You have a containerized service. You want it running in AWS. You create an ECS cluster, write a task definition, and hit deploy. A minute later, your container is up and serving traffic. You never touched a server. That convenience hides a remarkable amount of engineering. Somewhere in AWS, a scheduler decided where your task would run, a microVM was created and booted in milliseconds, a network interface was injected into your VPC, and your con… Read More

Explained: CoreDNS

You deploy a new service to your Kubernetes cluster. The pods come up healthy. You open a shell inside one of them and try to reach another service by name — http://payments-service — and nothing happens. Timeout. You try the full name: http://payments-service.billing.svc.cluster.local . Still nothing. You try the service's ClusterIP directly, and it works fine. Something in the cluster is resolving names, but it's not resolving yours. If … Read More

Architecture: Zscaler

You open your laptop at home, connect to the company network, and almost immediately a login prompt appears asking you to authenticate — again. Or a website you could access at the office is suddenly blocked. Or your IT team says "it goes through Zscaler" when you ask why something is slow. Zscaler is one of those pieces of infrastructure that affects every developer every day, but almost nobody understands how it actually works. This p… Read More