Study library
Learn like Educative — prep like Hello Interview
Browse structured tracks with free starter lessons in every category. Premium topics unlock the full interview library, Google SD collection, and AI tools.
- 30
- Total topics
- 11
- Free starters
- 19
- Premium topics
- 6
- Learning tracks
All categories
🔓 Free lessons open to everyone · 🔒 Pro unlocks interview-critical topics
Classic interviews, core concepts, and Google-scale architectures.
Non-Functional Requirements (NFR)
FreeScalability, security, performance, monitoring, availability, and reliability — why, where, how, and when with execution flows.
7 lessons · 2h · Beginner
System Design Fundamentals
FreeScalability, CAP, caching, load balancing, databases, CDN, and the 45-minute interview framework.
10 lessons · 2h 30m · Beginner
Design URL Shortener
FreeHashing, redirects, analytics, and storage trade-offs.
8 lessons · 55 min · Beginner
Design Rate Limiter
FreeToken bucket, sliding window, Redis, and distributed limits.
10 lessons · 1h 10m · Intermediate
Design ChatGPT System
ProLLM serving, context windows, caching, and guardrails.
12 lessons · 1h 25m · Advanced
31 Core Concepts
ProLoad balancing, sharding, CDN, messaging, Bloom filters, and more.
31 lessons · 6h · Intermediate
Google SD Collection
ProMaps, Gmail, Docs, Trends, Street View, and feature flags.
12 lessons · 4h · Advanced
Design News Feed
ProFan-out, ranking, caching, and celebrity problem.
11 lessons · 1h 15m · Advanced
Design Payment System
ProIdempotency, reconciliation, and exactly-once semantics.
12 lessons · 1h 20m · Advanced
Patterns, LeetCode-style problems, and coding interview scripts.
DSA Patterns Overview
FreeHow to recognize and apply the 14 essential patterns.
5 lessons · 40 min · Beginner
Two Pointers Pattern
FreeSorted arrays, sliding windows, and pair problems.
7 lessons · 50 min · Beginner
Top Interview Problems
ProCurated FAANG-style problems with walkthroughs.
25 lessons · 3h · Intermediate
LeetCode 25 Must-Do
ProHigh-frequency problems with pattern tags.
25 lessons · 2h 30m · Intermediate
Dynamic Programming Deep Dive
ProState machines, memoization, and interview templates.
18 lessons · 2h · Advanced
LLMs, RAG, agents, MCP, and AI system design.
Prompt Engineering Basics
FreeFew-shot, chain-of-thought, and evaluation.
4 lessons · 35 min · Beginner
RAG Fundamentals
FreeEmbeddings, retrieval, chunking, and vector stores.
8 lessons · 55 min · Intermediate
Agents & MCP
ProTool use, orchestration, and Model Context Protocol.
14 lessons · 1h 30m · Advanced
Fine-Tuning & LoRA
ProWhen to fine-tune, datasets, and deployment.
10 lessons · 1h 15m · Advanced
ML Interview Guide
ProML/DL fundamentals for technical screens.
16 lessons · 2h · Advanced
LangChain in Production
ProChains, memory, evals, and observability.
12 lessons · 1h 40m · Intermediate
Kafka, Spark, AWS, and distributed data systems.
Apache Kafka Basics
FreeTopics, partitions, consumer groups, and delivery semantics.
6 lessons · 45 min · Beginner
Apache Spark Fundamentals
ProRDDs, DataFrames, Spark SQL, and cluster modes.
11 lessons · 1h 20m · Intermediate
AWS Cloud Architect
ProVPC, S3, RDS, Lambda, and well-architected patterns.
22 lessons · 3h · Intermediate
Kubernetes for Engineers
ProPods, services, ingress, and production operations.
18 lessons · 2h 30m · Advanced
STAR method, leadership stories, and senior-level communication.
STAR Method Mastery
FreeStructure stories for impact, conflict, and leadership.
4 lessons · 30 min · Beginner
Top Behavioral Questions
Pro50+ questions with answer frameworks.
15 lessons · 1h 30m · Intermediate
Staff+ Promotion Stories
ProScope, influence, and executive communication.
8 lessons · 1h · Advanced
Core Java, collections, Spring, and backend interview prep.
Java Core Concepts
FreeOOP, generics, streams, and concurrency basics.
7 lessons · 50 min · Beginner
Java Collections Deep Dive
ProLists, maps, sets, and interview favorites.
10 lessons · 1h 15m · Intermediate
Spring Boot Interview Prep
ProDI, REST, security, and production patterns.
16 lessons · 2h · Intermediate