AWS
70 bites tagged AWS — interview questions with model answers, and 60-second explainers.
Managed Graph Databases: When Relationships Are the Data
A managed graph database models data as nodes and edges, making relationship-heavy queries fast. Use it for social networks, fraud detection, or recommendations.
Database Multi-AZ: High Availability vs. Read Scaling
Multi-AZ deployment is like a hot spare database in another datacenter for automatic failover. It's for critical systems where downtime is costly. The footgun is assuming all standbys serve reads; only the 'cluster' type does, not the 'instance' type.
Managed Database Backups: Your Cloud's Undo Button
Think of managed backups as your cloud provider's automated safety net for your database. It periodically saves snapshots, letting you restore to a point in time after a failure.
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.
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.
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).
VPC: Your Private Slice of the Public Cloud
A Virtual Private Cloud (VPC) is your private, fenced-off section of a public cloud. You use it to launch resources like servers and databases in a logically isolated network, controlling all traffic.
Cross-Region Replication (CRR): Geographic Data Copying
Cross-Region Replication automatically copies data to another geographic region, like a live backup. Use it for disaster recovery, lower latency for global users, or compliance. The footgun: it only copies *new* objects, not what's already in the bucket.
AWS Dedicated Hosts: Your Own Physical Server in the Cloud
An AWS Dedicated Host is your own physical server in the cloud, providing single-tenant hardware. Use it for "bring your own license" (BYOL) software tied to physical cores, or for compliance rules that forbid multi-tenancy.
AWS Placement Groups: Control Where Your Instances Run
AWS Placement Groups let you control where EC2 instances run relative to each other. Use a Cluster group for low-latency HPC, or Spread/Partition groups to reduce correlated hardware failures. The main footgun is picking the wrong strategy for your workload.
Spot Instances: Trade Reliability for Huge Cost Savings
Spot Instances let you use spare AWS compute for up to 90% off. They're great for fault-tolerant jobs like batch processing or CI/CD. The footgun: AWS can reclaim your instance with a two-minute warning, so don't use them for critical workloads.
User Data Scripts: Day-One Instance Configuration
User data scripts are your instance's "Day One" instructions, automatically running commands like package installs on first boot. Use it to set up a web server or install agents without manual SSH.
AWS Reserved Instances: Commit to Compute, Save Big
Reserved Instances are like leasing a car instead of renting daily: commit to 1-3 years of compute for a steep discount. They're ideal for predictable, steady-state workloads. The footgun is buying inflexible Standard RIs when your needs might change.
Auto Scaling Groups: Elasticity and Self-Healing
An Auto Scaling Group (ASG) is like a thermostat for your servers, automatically adding or removing instances to match demand and replacing any that fail. Use it for web apps with variable traffic or services that need to self-heal from instance failures.
Cloud Instances: Renting Servers on Demand
Think of a cloud instance as renting a virtual computer. Instead of buying hardware, you launch a pre-configured virtual machine to run your applications, paying only for what you use. This is ideal for applications that need to scale up or down with demand.
Machine Images: The Blueprint for Your Servers
A machine image is a server blueprint, packaging an OS and software into a template for launching identical virtual machines. It's used for auto-scaling and creating consistent environments.
Public Cloud: Renting, Not Owning, Your Datacenter
Public cloud is like renting computing power instead of owning a datacenter. You get on-demand access to a shared pool of resources like servers and storage, paying only for what you use. The main footgun is cost; uncontrolled usage leads to surprise bills.
AWS Secrets Manager: Stop Hardcoding Credentials
AWS Secrets Manager is a digital vault for your app's credentials. Instead of hardcoding API keys or database passwords, your app fetches them at runtime. It's used for storing sensitive data securely, with built-in rotation and auditing.
AWS CloudFormation: Your AWS Infrastructure as a Blueprint
AWS CloudFormation is your infrastructure's blueprint. Declare AWS resources in a YAML/JSON file, and AWS builds it. This is perfect for creating repeatable, version-controlled environments.
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