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Lessons (31)

• Batch vs Stream and Data Modeling

  … bounded set later; streaming handles events continuously while data modeling controls read and write cost](/img/system-design …

• MVC, MVP & MVVM

  … They differ in the "middle piece" and in how data flows. MVC: Model–View–Controller Invented at Xerox …

• CQRS & Event Sourcing

  … They return data and change nothing. ![CQRS: a write model for commands, a read model for queries, synced …

• Onion Architecture & Clean vs Hexagonal vs Onion

  … Infrastructure (databases, UI, frameworks) is the outer skin . ![Onion architecture: rings around the domain model](/img/architecture/onion …

• Finding Service Boundaries with DDD

  … own model. - A bounded context is the natural boundary for a microservice, with its own data and language …

• What Is Software Architecture?

  … the C4 model The C4 model (Simon Brown) draws architecture at four zoom levels, like a map app …

• Vertical Slice Architecture & the Modular Monolith

  … uses a rich domain model export async function placeOrder(deps: { orders: OrderRepository; events: EventBus }, cmd: PlaceOrderCommand) { const order …

• Choosing an Architecture

  … Onion · Vertical slices"] Q3["3️⃣ Domain modelling<br/ How do we model the business?"] -- A3["DDD strategic (boundaries …

• Normalization & Denormalization

  … read model is worth it. The goal: one fact, one home Normalization organizes a relational database so a …

• System Design Interview Framework

  … 4. Model data and name each source of truth. 5. Define APIs with authorization and idempotency. 6. Deep …

• Database Relations & Foreign Keys

  Model one-to-one, one-to-many and many-to-many data with keys, constraints and deletion rules …

• Time, Consistency and Distributed Transactions

  … CRDTs converge without coordination for suitable mergeable data; operational transformation resolves collaborative edits with an explicit transformation model.

• Domain-Driven Design: Tactical Patterns

  … customer)); } } Anaemic vs rich domain model ts // ❌ Anaemic: a bag of data; the rules live somewhere else (and …

• Event-Driven Architecture

  … CQRS Events keep separate read models up to date Write model publishes; read model projects Fast, tailored reads …

• DBMS Foundations, Keys & Normalization

  … keys identify records, dependencies guide normalization, and constraints enforce relationships](/img/database-interviews/foundations.svg) Q2, Q3 and …

• Clean Architecture in Depth

  … Web frameworks, databases, UIs and third-party APIs are the cabins and paint: details that plug in from …

• Trees & Binary Search Trees

  Trees model hierarchies like folders, the DOM and org charts. Learn the vocabulary, the four traversals, and how …

• Kafka vs RabbitMQ & the Kafka Ecosystem

  … databases (Debezium CDC), S3, MQTT, Salesforce. - Sink connectors push data out : Elasticsearch, S3, Snowflake, BigQuery, MongoDB, Postgres. json …

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

  … easy for everyone, fits every accessory (data science, AI), not the fastest. - Rust 🏎️ = a race car: top …

• Layered (N-Tier) Architecture

  … placeOrder() Persistence (data access) Read and write data Repositories, ORM models, SQL Database Store data PostgreSQL, MongoDB mermaid …

• SQL vs NoSQL Databases

  … Model for your queries. In document databases, you design documents around how the app reads data. Data that …

• Authentication, Authorization & API Security

  … It is the recommended flow for web, mobile and single-page apps. Authorization models Model Idea Example --- --- --- RBAC …

• Data in Microservices: Sagas & the Outbox Pattern

  … API composition, replicated data, or CQRS read models.

• Structural Patterns: How to Connect Objects

  … Every oak shares one 3D model and texture; each tree only stores its own position. Problem: huge numbers …

• YAGNI: You Aren't Gonna Need It

  … fine - Hard-to-reverse decisions: database choice, public API shape, data model, security. Think these through. - Known, committed …

• React vs Vue vs Angular

  … Simple mental model; sometimes needs memoisation. - Vue wraps state in Proxies (remember the Proxy pattern?) and tracks exactly …

• Monolith vs Microservices

  … run it" model). Key takeaways - Monolith = one deployable; microservices = independently deployable services, each owning its data. - Microservices buy …

• Message Queues & RabbitMQ

  … an API is down); some fail forever (bad data). Don't retry forever, and don't lose them …

• TypeScript Essentials

  … unions: model states safely ts type RequestState<T = { status: "loading" } { status: "error"; error: string } { status: "success"; data: T …

• Serverless Architecture

  … else handles the car. Serverless is the taxi model for computing: you write functions, the cloud runs them …

• Hexagonal Architecture (Ports & Adapters)

  … the database is at the bottom"] direction TB L1[UI] -- L2[Business] -- L3[(Database)] end subgraph Hex["Hexagonal …