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Lessons (40)

• Architecture Patterns at Scale

  Choose client-server, microservices, serverless, event-driven or peer-to-peer architecture based on ownership, failure boundaries and …

• Rust: Ownership, Borrowing and Lifetimes

  … Nobody may keep a borrowed book after the owner has returned it. ![Ownership: one owner; many shared borrows …

• Scalable Frontend Architecture

  Structure a growing frontend around features, clear ownership and stable boundaries so teams can add product work without …

• Time, Consistency and Distributed Transactions

  … clocks order observations, fencing protects ownership, and sagas compensate cross-service work](/img/system-design-l6/time-transactions …

• Design a Ride-Sharing Service

  … Check the assignment version before accepting; a delayed message must not revive stale ownership. How to prove it …

• Product-Scale Frontend Patterns

  … it is only queued. Feature flags need lifecycle ownership Flags decouple deployment from release, but old flags become …

• Cross-Service Data: How to Join Without a Database JOIN

  … It protects independent deployment, schema ownership and service autonomy. The answer is not to create a shared database …

• Reusable Modules and Clear Interfaces

  Build and call a small module, expose outputs, and define sensible module ownership and versioning. A module is …

• Imports, Moved Blocks, and Safe Refactoring

  Adopt existing infrastructure, rename resources without recreating them, and remove ownership deliberately. Import brings an existing object under …

• Distributed Coordination: Consensus, Heartbeats and Gossip

  … Verify stale writes are rejected and ownership recovers within the target interval. Observe term changes, quorum loss and …

• Capacity, Availability, Latency and CAP

  … Refuse or defer a write when safe ownership cannot be established. Walk through a failure and recovery Both …

• Authentication, Authorization & API Security

  … shared with you" (Google Docs) js // Always check ownership, not just "is logged in" app.get("/orders/:id …

• Rust: Types, Errors and Concurrency

  … Arc for shared ownership, Mutex for safe mutation let counter = Arc::new(Mutex::new(0)); let handles: Vec …

• Views, Triggers & Stored Procedures

  … Prefer set-based updates, clear ownership and auditability. Use triggers for local data rules, not cross-service workflows …

• Go Concurrency: Goroutines, Channels and Context

  … Channels Passing ownership of data, signalling, pipelines 💡 Channels or mutex? Use channels to transfer ownership or coordinate stages …

• Atomic Design & Component Libraries

  … design tokens, interaction rules, accessibility requirements, documentation, and ownership. The five levels Level Responsibility Example Should it know …

• Resilience, Disaster Recovery and Multi-Region Design

  … Define fencing, write ownership, and reconciliation deliberately. For global tables, choose the intended consistency mode rather than assuming …

• Batch vs Stream and Data Modeling

  … totals and fresh risk signals using explicit data ownership and lateness rules. Practical response 1. Keep transactional purchase …

• Domains, Load Balancers and HTTPS

  … Request a certificate for your domain, validate ownership by DNS, then attach it to the HTTPS listener. Check …

• Environments, Workspaces, and Multiple Accounts

  Separate development and production ownership, understand workspace limits, and configure provider aliases. Isolation has several layers Development and …

• AWS Security Building Blocks

  … After verifying a token, use the verified user identity to enforce ownership. Do not trust a browser's …

• Dependencies, Data Sources, and Resource Lifecycle

  … Use it only when ownership is explicitly shared, such as an autoscaler owning desired capacity. Exercise Create the …

• Data Structures for Scale

  … Never use a Bloom-filter positive as proof of authorization or inventory ownership. Examples that show the trade …

• Real-Time, Pub/Sub, Webhooks and CDC

  … to many internal consumers Define retention and consumer ownership CDC Publish committed database changes Use an outbox/transaction …

• Database Relations & Foreign Keys

  … real business facts. Start from the real-world ownership rule A relation is not an ORM decoration. It …

• Database Internals, Replication and Scaling

  … proxy if needed. Hot write row Redesign counter/ownership, not just replicas. Analytics hurts writes Send it to …

• API Contracts, Gateways and Security

  … The fix is an ownership-scoped query or policy check at the resource boundary, not another token check …

• Caching, Consistent Hashing and Sharding

  … Avoid confusing cache placement with durable data ownership. Practical response 1. Cache product reads with a defined freshness …

• Storage, Search and Location Queries

  … Store photo bytes in object storage and keep ownership plus publication state in transactional metadata. 2. Build text …

• Multi-Region and Disaster Recovery

  … Active-active means multiple regions write concurrently; it needs conflict resolution, request routing and careful ownership. Do not …

• Flash Sale: 10 Million Buyers, No Oversell

  … Admission controls pressure but grants no inventory ownership. 2. Create a reservation using a conditional stock update and …

• Drift, Troubleshooting, and Disaster Recovery

  … or separate lifecycle stages Resource already exists Import ownership, wrong state key, duplicate root Find the owner before …

• Design a URL Shortener

  … Either option is fine when the durable database—not cache memory—decides ownership. Failure cases that change the …

• AWS Interview Questions: Clear Answers

  … Keep the database private, scope the API's IAM role, and enforce customer ownership inside application authorization. Add …

• The L6 System-Design Thinking Loop

  … be stale? Browse counts and recommendations, not seat ownership. What is shed first? Analytics, email, previews, then low …

• C4 Architecture Diagrams: Context, Container, Component and Code

  … Stripe, an email provider and a customer browser affect your system, but they are outside its ownership boundary …

• Production Capstone and Interview Practice

  … Split carefully; excessive fragmentation creates dependencies and operational overhead. Completion criteria: private storage, clear ownership, isolated environment credentials …

• Backend Languages: Node.js, Go, Python & Rust

  … axum::serve(listener, app).await.unwrap(); } Rust's ownership system catches memory bugs and data races at compile …

• Choosing a Programming Language

  … collected Garbage collected (ref counting + GC) Garbage collected Ownership , no GC Concurrency Event loop + async/await asyncio , threads …

• REST API Design

  … or /Order Items . - Nest only one level for ownership: /users/42/orders ✅, /users/42/orders/9/items/3 …