Architecture
376 bites tagged Architecture — interview questions with model answers, and 60-second explainers.
CQRS: Separate Models for Reading and Writing Data
CQRS splits your application into two parts: one for changing data (Commands) and one for reading it (Queries), often with separate data models. Use it in complex systems with different read/write patterns.
Serverless State Machines: The Conductor for Your Functions
A serverless state machine is the conductor for your microservices, telling each function when to run and how to handle errors. It's built for multi-step processes like ETL pipelines or coordinating parallel tasks. The footgun is creating a visual monolith.
The Fan-out Pattern: One Message, Many Receivers
The fan-out pattern uses a single message to trigger multiple parallel actions, like a press conference where one announcement reaches many reporters. Use it for events like a new user signup that triggers emails, analytics, and fraud checks.
Serverless Cold Starts: The Price of 'Pay-per-Use'
A serverless cold start is the initial delay when a function boots from scratch, like waking a computer from being off versus asleep. It happens on the first request or after inactivity.
API Gateway: The Front Door for Your Microservices
An API Gateway is the single front door for all your backend services. It handles tasks like authentication and rate limiting before routing requests to the correct microservice. The footgun is treating it as a simple proxy; it can become a bottleneck.
Kubernetes Control Plane: The Cluster's Brain
The Kubernetes control plane is the cluster's brain, making all global decisions like scheduling pods and responding to events. You interact with it via `kubectl` to manage your applications. The footgun: never run your own workloads on control plane nodes.
Immutable Deployments: Treat Servers Like Cattle, Not Pets
Treat servers like cattle, not pets. Instead of modifying live servers, you deploy updates by replacing entire server fleets with new, pre-baked images. This eliminates configuration drift and simplifies rollbacks.
The Twelve-Factor App: A Blueprint for Portable Cloud Apps
The Twelve-Factor App is a blueprint for building portable, resilient cloud apps. It's used for microservices or apps on platforms like Kubernetes, ensuring they can be easily deployed and scaled. The footgun is treating it as dogma, not a guide.
Serverless Databases: Pay for Use, Not for Idle
A serverless database automatically scales compute and storage based on demand, from zero to massive, without you managing any servers. Use it for spiky, unpredictable workloads to avoid paying for idle capacity.
Managed Document Databases: Your Data, Their Ops
A managed document database is like a fully-staffed warehouse for your data. You store JSON-like objects, and the provider handles security, maintenance, and scaling. It's the default for cloud apps, but the convenience isn't free—watch for surprise bills.
Cloud Compliance Frameworks: Security as a Standard
Think of a cloud compliance framework as a standardized rulebook for security. It translates broad security goals into specific, auditable controls, providing a checklist to prove your cloud environment is secure to regulators and customers.
Data Sovereignty: Your Data's Legal 'Citizenship'
Data sovereignty means data is subject to the laws of the country it's in; data residency is storing it there to comply. This is critical for apps in regions with strict laws like the EU's GDPR. The footgun is confusing residency with full legal compliance.
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.
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.
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.
FaaS: Run Code, Not Servers
FaaS lets you run code without managing servers, like renting a contractor for one task. It's ideal for event-driven actions like processing uploads or handling webhooks. The footgun is cost: for high, steady traffic, a dedicated server is often cheaper.
Multi-cloud: Spreading Bets Across Cloud Providers
Multi-cloud is a strategy for using services from two or more cloud providers to avoid vendor lock-in. It's used to cherry-pick best-in-class services or improve resilience. The footgun is underestimating the complexity of managing disparate APIs and security.
Cloud Regions and AZs: Infrastructure Built for Failure
Think of a cloud region as a city and its availability zones (AZs) as independent power grids. If one AZ fails, your app runs in another. The footgun is deploying to a single AZ; this provides no protection against data center-level outages.
High Availability: Designing Systems That Don't Go Down
High Availability (HA) means designing systems to survive failures by having redundant components ready to take over instantly. It's essential for services like payment gateways where downtime costs money and user trust.
Cloud Scalability vs. Elasticity: Planned Growth vs. Real-Time Reaction
Think of scalability as adding lanes to a highway for long-term growth. Elasticity is opening a reversible lane only during rush hour. Scalability handles predictable demand, like a product launch; elasticity manages unpredictable spikes, like a viral post.
The Twelve-Factor App: Store Config in the Environment
Your app's code is the blueprint; its config is the specific address and utility hookups. Store config—database URLs, API keys—in environment variables, not in the code. The footgun is hardcoding secrets, making your code base impossible to open-source safely.
Manual Dependency Injection: No Frameworks, Just Code
Manual dependency injection means you are the 'framework,' creating and passing dependencies yourself via constructors. It's great for simple apps where a full DI library is overkill, but the footgun is creating dependencies inside the class that needs them.
The Testing Pyramid: Fast Feedback, Low Cost
The Testing Pyramid guides test suite structure: a wide base of fast unit tests, a smaller middle of integration tests, and a tiny top of slow UI tests. This model is key for Android's local, instrumented, and UI tests. The footgun is inverting it.
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