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Lessons (40)

• Big-O Notation Made Simple

  Big-O describes how an algorithm's time or memory grows as the input grows. Learn the 7 …

• Big Data: ETL, Warehouses and Streaming

  … Choose based on team operations and freshness needs, not fashion. Record lineage, schema evolution, data quality checks and …

• SQL vs NoSQL Databases

  … places ORDER -- { ORDER ITEM : contains PRODUCT --o{ ORDER ITEM : "appears in" CUSTOMER { bigint id PK text email text …

• Arrays & Strings

  … when full, the engine allocates a bigger block (often 2×) and copies everything over. That copy is O …

• Heaps & Priority Queues

  … or removes items in O(log n). The engine behind "top K" problems, schedulers and Dijkstra. The big …

• Stacks & Queues

  … Fine for small arrays; slow for big queues. An O(1) queue js class Queue { items = new Map …

• Choosing an Architecture

  … Watch out for --- --- --- --- Monolith One deployable Early products, small teams Turning into a big ball of mud Modular …

• React vs Vue vs Angular

  … comparison of reactivity, templates, state and tooling, and a simple way to choose between them. The big idea …

• React Fundamentals

  … small, reusable bricks ( components ) snap together into bigger ones, and the bigger ones form the whole page. And …

• Dynamic Programming

  DP means solving a big problem by remembering the answers to its smaller overlapping sub-problems. A friendly …

• What Is Software Architecture?

  Architecture is the set of big decisions that are expensive to change later. Learn quality attributes, trade-offs …

• Sorting Algorithms

  … That matters when you sort by several keys. The simple O(n²) sorts Bubble sort: big items "bubble …

• Vertical Slice Architecture & the Modular Monolith

  … The Modular Monolith The big idea An apartment building is one structure with one foundation and one address …

• Scaling, Load Balancing & Rate Limiting

  … free one → horizontal scaling (scale out) with a load balancer . ![Vertical scaling makes one server bigger; horizontal scaling …

• Scaling & Health Probes

  … Autoscaling The big idea A supermarket opens more checkout lanes when the queues get long, and closes some …

• Frontend Performance & Core Web Vitals

  … yield() or setTimeout ). - Move heavy work off the main thread: Web Workers for parsing, image processing, big calculations …

• DSA Interview Patterns Cheat Sheet

  … O(n log n) or O(n) Sorting, heap, hash map, two pointers bigger O(log n) or …

• Kafka vs RabbitMQ & the Kafka Ecosystem

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

• Two Pointers & Sliding Window

  … into O(n). Learn them with animated-style diagrams and classic interview examples. Two Pointers The big idea …

• What Are Design Patterns?

  … Meet the three families and learn how to use patterns without overusing them. The big idea Architects don …

• Kafka Producers

  … idempotent producer. The big idea A postal worker doesn't drive to the sorting office for every single …

• Database Indexing & Transactions

  … a range on created at) --- Part 2: Transactions and concurrency The big idea Two people try to book …

• YAGNI: You Aren't Gonna Need It

  … C3,C4 cost The 4th cost is the big one: when the need finally arrives, it is almost …

• Timeouts, Retries & Backpressure

  A slow dependency should consume a bounded budget, not create an infinite retry storm. The big idea A …

• Small Functions That Do One Thing

  … insert)] W -- T[welcomeTemplate] One level of abstraction per function Don't mix "big picture" steps with tiny …

• What Is Apache Kafka?

  … log of events that many systems can write to and read from at huge scale. The big picture …

• Premiere-Night Video Streaming

  Let millions press Play together by separating small control-plane APIs from CDN-delivered video bytes. The big …

• Domain-Driven Design: Strategic Design

  … to discover them. The big idea Software fails most often not because of bad code, but because developers …

• Delivery Guarantees: At-Most, At-Least & Exactly Once

  … toLedgerEntry(message.value) }] }); await tx.sendOffsets({ consumerGroupId: "ledger-writer", topics: [{ topic, partitions: [{ partition, offset: (BigInt(message.offset) + 1n …

• Topics, Partitions & Offsets

  … ordering, how offsets work, and how retention and compaction clean up. The big idea A supermarket with one …

• The L6 System-Design Thinking Loop

  … and measure recovery. The big idea An L6 answer is not a list of technologies. It explains what …

• Binary Search

  … If capacity C works, every bigger capacity works too, so the condition flips once. Binary search the capacity …

• API Gateway, BFF & Service Discovery

  … API gateways, Backends for Frontends, service registries, and service meshes. The big idea A big hotel has one …

• Consumers & Consumer Groups

  … consumer.commitOffsets([ { topic, partition, offset: (BigInt(message.offset) + 1n).toString() }, // commit the NEXT offset ]); }, }); ⚠️ Auto-commit (the default …

• Trees & Binary Search Trees

  … fast lookups. The big idea A family tree or a company org chart : one person at the top …

• State Management (Redux, Zustand, TanStack Query)

  … The biggest mistake is putting everything in one global store. ![Four kinds of state and where each belongs …

• ConfigMaps, Secrets & Storage

  … ExternalSecret YAML<br/ (no real values)"] -- ESO[operator] ESO -.reads.- V --- Part 2: Storage The big idea Containers …

• JavaScript Essentials: Event Loop, Closures & this

  … The event loop The big idea JavaScript has one thread : it can do only one thing at a …

• REST API Design

  … Pros Cons --- --- --- --- Offset ?page=3&limit=20 Simple, jump to any page Slow on big tables; items shift …

• CQRS & Event Sourcing

  … Powerful patterns, explained simply, with honest trade-offs. Part 1: CQRS The big idea A restaurant kitchen and …