Cloud
189 bites tagged Cloud — interview questions with model answers, and 60-second explainers.
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.
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).
Cloud Subnets: Your Virtual Network's Neighborhoods
Think of a subnet as a neighborhood in your virtual network (VPC), giving a block of IP addresses to a group of resources. Use them to isolate web servers from databases or apply specific firewall rules.
CIDR: Flexible IP Address Blocks
CIDR groups IP addresses into flexible blocks, replacing rigid A/B/C classes. You use it to define network ranges like `10.0.0.0/16` for a VPC. The footgun: a smaller slash number like /16 means a *larger* network than a bigger number like /24.
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.
Storage Gateway: Your On-Prem to Cloud Translator
A storage gateway is a translator, letting your on-prem applications talk to cloud storage without learning its native API language. It presents cloud storage as a local file share or block device, enabling hybrid cloud backups and data tiering.
Presigned URLs: Temporary Access to Private Files
A presigned URL is a temporary, authenticated link to a private cloud storage object, bundling credentials into the URL. Use it to let users upload or download private files directly, bypassing your server. The URL is a bearer token, so set short expirations.
Object Versioning: A Safety Net for Cloud Files
Object Versioning treats every file change as a new version, not a replacement. It's used in cloud storage to recover from accidental overwrites or deletions. The footgun: you pay for all versions, so costs can multiply without cleanup policies.
Encryption at Rest: Securing Your Data When It's Not Moving
Encryption at rest is like locking your data in a safe when it's not moving. It protects raw files on disk if storage is stolen, a default on platforms like Google Cloud. The footgun: it doesn't stop a compromised app with valid keys from reading.
Block Storage Snapshots Are Incremental Backups
A snapshot is an incremental, point-in-time backup of a disk volume, saving only changed data blocks. Use it for disaster recovery to restore a volume's exact state. The footgun: deleting an older snapshot may not save money if a newer one needs its data.
Cloud Storage Tiers: Match Cost to Access Frequency
Storage tiers match data cost to access frequency. 'Hot' tiers are fast and expensive for active files; 'cold' tiers are cheap for archives. Use for data that cools over time, like logs. The footgun: retrieving cold data unexpectedly is slow and costly.
Data Durability vs. Availability: Lost vs. Unreachable
Availability is "can I reach my data right now?" while durability is "will my data still exist tomorrow?". Cloud storage systems are designed for both, but they solve different problems: network outages vs. data corruption.
Cloud File Storage: A Shared Drive on the Internet
Think of cloud file storage as a shared network drive, but managed by a provider and accessible over the internet. It's for shared content, user home directories, and apps needing a traditional file system.
Block Storage: Your Virtual Hard Drive in the Cloud
Think of block storage as a raw hard drive in the cloud. It's the foundation for virtual machine disks (like AWS EBS) and databases that need direct control over their storage. The footgun is treating it like a web-accessible file share; it's a raw device.
Object Storage: Data Without a File Hierarchy
Object storage is like a valet system for data. You get a unique ID for a self-contained 'blob' of data and metadata, instead of navigating a file path. It's the backbone of cloud storage (like S3) for images and backups. The footgun: objects are immutable.
Bare Metal Instances: Your Own Dedicated Cloud Server
A bare metal instance is your own dedicated physical server in the cloud—no sharing, no virtualization layer. Use it for workloads needing direct hardware access or for licensing that forbids VMs. The footgun: you trade cloud elasticity for this control.
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.
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