Networking
137 bites tagged Networking — interview questions with model answers, and 60-second explainers.
Kubernetes LoadBalancer: Your App's Public Entry Point
A Kubernetes LoadBalancer Service automatically provisions a cloud provider's load balancer to expose your app externally. It's the simplest way to get a public IP, but creating one per service is expensive and inflexible. Use an Ingress for more control.
Ingress Controller: Your Cluster's Smart Reverse Proxy
An Ingress Controller is the traffic cop for your Kubernetes cluster, directing external HTTP/S requests to the correct internal services. It exposes multiple services under a single IP, handling host and path routing.
Kubernetes Ingress: The Cluster's Smart Receptionist
Ingress acts as a smart receptionist for your cluster, routing external HTTP/S traffic to internal services based on host or path. This lets you expose many apps with one load balancer.
Kubernetes DNS: How Pods Find Each Other
Kubernetes DNS gives services and pods stable, human-readable names so you don't have to track ephemeral IP addresses. It's how a frontend pod finds a backend service.
ClusterIP Service: Internal-Only Networking
A ClusterIP service is like an unlisted phone number for your pods, providing a stable internal IP for communication *within* the cluster. Use it for backend-to-backend traffic. The footgun is assuming it's reachable from the outside—it's not.
Docker Compose Networking: How Services Talk to Each Other
Docker Compose puts your services on a private network, letting them communicate using service names as hostnames. This is how a 'web' container finds your 'db' container. The footgun is using `localhost`; always use the service name for inter-container calls.
Docker Networking: How Containers Talk to Each Other
Docker gives each container its own isolated network, preventing port conflicts. Containers connect via networks, like `bridge` for local communication. For containers to find each other by name, you must use a user-defined bridge network; the default one…
gRPC: High-Performance RPC with Contracts
gRPC is a typed, high-performance function call between services. Instead of crafting JSON, you define a contract and gRPC handles the efficient binary transport. It's for low-latency microservice communication.
Email Spam: The Origin of Junk Mail
Email spam is any unsolicited message sent in bulk. Named after a Monty Python sketch for its intrusive nature, it grew to comprise 90% of all email by 2014, making spam filters a universal necessity.
The Ambassador Pattern: Your App's Diplomatic Sidecar
The Ambassador pattern places a proxy next to your application to handle its network communication, like a diplomat. This adds modern features like monitoring, security, and retries to legacy apps or across languages without changing app code.
Zero Trust: Never Trust, Always Verify
Zero Trust assumes no user or device is safe by default, even on a 'trusted' corporate network. It's like needing a keycard for every door, not just the front gate. The biggest mistake is thinking you can buy a 'Zero Trust' product; it's a strategic.
DDoS Mitigation: Surviving Traffic Floods
DDoS mitigation acts like a smart bouncer, learning your app's normal traffic to block malicious floods. It's used for any public internet endpoint, filtering attacks at the network and transport layers (L3/L4).
Web Application Firewall (WAF): Your App's HTTP Bodyguard
A Web Application Firewall (WAF) is a specialized bodyguard for your web app, inspecting all HTTP traffic for malicious requests. It blocks common attacks like SQL injection and XSS by matching traffic against known patterns.
Encryption in Transit: Protecting Data on the Move
Encryption in transit acts like a locked box for data moving across a network. It secures everything from website connections (HTTPS) to data moving between services inside a cloud network.
Global Server Load Balancing (GSLB): DNS for High Availability
Global Server Load Balancing (GSLB) uses DNS to route users to the best data center, not just the best server. It considers geography, health, and load to provide disaster recovery and lower latency.
Cloud Direct Connect: A Private Lane to the Cloud
Think of Direct Connect as a private fiber-optic highway from your datacenter to the cloud, bypassing the public internet. It's for stable, high-bandwidth needs like large data transfers where public internet performance is too unpredictable or insecure.
DNS Routing Policies: Directing Traffic with Intention
DNS routing policies are a control plane for your domain, directing users based on location, latency, or server health. Use them for disaster recovery (failover) or canary releases (weighted). The footgun: confusing geolocation with latency-based routing.
Load Balancer Health Checks: Don't Route to Dead Servers
A load balancer uses health checks to ask backend servers "Are you alive?" before sending them traffic. This is essential for any high-availability setup, preventing users from being routed to a crashed or unresponsive instance.
VPC Peering: Connect Private Networks Securely
VPC peering connects two virtual networks as if they were one, letting them talk over private IPs. Use it to share files or access resources between VPCs across accounts or regions without going over the public internet.
Network ACLs: A Stateless Firewall for Subnets
A Network ACL (NACL) is a firewall for an entire cloud subnet, checking traffic as it enters or leaves. It's used for broad, stateless rules, like blocking a malicious IP from all instances.
NAT Gateway: Your VPC's Outbound-Only Internet Door
A NAT Gateway is a one-way door for your private cloud resources. It lets instances in private subnets initiate outbound traffic to the internet—like for updates or API calls—but blocks unsolicited inbound connections.
Managed Cloud DNS: Offload Your DNS Server Management
Managed Cloud DNS is DNS-as-a-service, letting you publish records without managing servers. Use it for public domains or private name resolution in your VPCs.
Content Delivery Network (CDN): Serving Content from the Edge
A CDN is like a global chain of convenience stores for your website's assets. It caches copies closer to users for faster delivery, speeding up images, CSS, and video. The footgun: accidentally caching private user data and serving it to everyone.
Security Groups: Stateful Firewalls for Your Cloud Resources
A security group is a stateful firewall for your cloud resources, like a bouncer with an allow-list. Use it to let a web server accept traffic or a database talk to app servers. The footgun: opening SSH to the entire internet (0.0.0.0/0).
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