The Code NotebookNotebook
Crack your next engineering interview
New video every dayFree courses for software engineers: system design, microservices, data science and DSA in Java. Every video comes with handwritten-style notes, from a Java developer with 7 years at a product company.
Java backend developer · teaching what actually gets asked
Free courses
All courses →Every video has a lesson page with its chapters and a notes PDF. Create a free account to open the notes and track your progress.
System Design
The foundations of system design for interviews: the 7-step framework, estimation, scaling, availability, CAP, networking, load balancers, CDNs, APIs, databases, indexes, replication, and data at scale: sharding, transactions, caching and object storage.
View the course
Microservices
Monolith to microservices, step by step: when not to use them, domain-driven design, the strangler fig, REST vs gRPC, events, Kafka, API gateways, service discovery, database per service, and saga, CQRS, outbox and circuit breakers.
View the course
Data Science
What a data scientist really does, the end-to-end workflow, NumPy in one lab, and the daily toolkit: pandas, SQL and data cleaning. Built around real datasets.
View the courseDSA in Java
Big-O, recursion, arrays, strings, hashing, linked lists, stacks, queues, binary search and trees, with Java code and LeetCode practice lists.
View the courseLatest on the channel
All videos →
4:27LeetCode Linked List Patterns in Java: 5 Interview Templates
Reverse, slow & fast pointers, cycle detection and more: the five templates that cover most linked list questions.
5:266 Array Patterns That Solve Most Interview Questions
5:41How Does XOR Find the One Unpaired Number?
6:508 Math Tricks Every Coder Gets Asked About
4:37Why Does Recursion Make Sense Once You Draw the Call Stack?
4:51Which Java Collection Should You Use? The Rules That Decide
6:46How Do You Know an Algorithm Is Slow Before You Run It?
📓 Notes for every video
A handwritten-style notes PDF for every lesson: diagrams, tables, code and interview questions.
✅ Track your progress
Create a free account and tick off videos from your dashboard.
🎯 Interview-first
Edge cases, follow-up questions and traps interviewers actually use.
Never miss a lesson
New lessons every week on YouTube, Shorts every day, and quick revision on Instagram.
Start a course today
Four free courses, one notebook. New lessons are added as they go live on YouTube. Pick one and work through it in order.