Engineering Knowledge Base

A practical, continuously growing knowledge base for software engineers — built for faster learning, better technical decisions, and focused interview preparation.

How to use this site: Pick a learning path below, follow the sections in order, and connect each concept to a real implementation or design scenario. Use the sidebar to navigate between topics.

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🗺️ Learning Paths Overview

Path	What It Covers	Best For
💼 Interview Preparation	System design, Java, behavioral, patterns	Upcoming interviews
📊 DSA Coding Training	20-week structured algorithm training	LeetCode & coding rounds
📚 Engineering Books	Key takeaways from essential books	Deep, long-term growth
☁️ Cloud Certifications	AWS DVA-C02 exam prep	Cloud developer cert

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💼 Interview Preparation Roadmap

A structured path for engineers targeting backend, system design, and Java/Spring interviews.

Phase 1 — Foundations

#	Topic	Key Concepts	Link
1	Java Fundamentals	Types, OOP, generics, exceptions, memory model	→ Java Overview
2	OOP Principles	Encapsulation, inheritance, polymorphism, interfaces	→ Java OOP
3	Java Collections	List, Map, Set, Queue, complexity trade-offs	→ Collections
4	Concurrency	Threads, locks, executors, CompletableFuture	→ Concurrency
5	JVM Internals	Memory areas, GC, class loading, JIT	→ JVM
6	SOLID Principles	Single responsibility through dependency inversion	→ SOLID
7	Design Patterns	Creational, structural, behavioral patterns	→ Design Patterns

Phase 2 — System Design

#	Topic	Key Concepts	Link
1	Interview Framework	How to approach a system design question	→ Framework
2	Architecture Fundamentals	Monolith vs microservices, trade-off model	→ Architecture
3	Distributed Systems	CAP theorem, consistency, partitioning	→ Distributed Systems
4	Consistent Hashing	Rings, virtual nodes, replication	→ Consistent Hashing
5	Caching Strategies	Cache-aside, write-through, eviction policies	→ Caching
6	Message Queues	Kafka, SQS, async patterns, ordering guarantees	→ Message Queues
7	API Design	REST, versioning, rate limiting, idempotency	→ API Design
8	Load Balancing	Strategies, health checks, failover	→ Load Balancing
9	Scaling Reads	Read replicas, CDN, sharding patterns	→ Scaling Reads
10	Scaling Writes	CQRS, event sourcing, write-behind	→ Scaling Writes
11	Observability	Metrics, tracing, logging, alerting	→ Observability
12	Security Patterns	Auth, zero trust, secrets management	→ Security Patterns
13	Microservices Patterns	Saga, circuit breaker, service mesh	→ Microservices
14	Common Interview Questions	URL shortener, Twitter, payment system	→ Interview Questions

Phase 3 — Domain Depth

Domain	Key Topics	Link
Database	ACID, indexes, transactions, replication, NoSQL vs SQL	→ Database
Kafka	Topics, partitions, consumer groups, Kafka Streams	→ Kafka
Redis	Data structures, pub/sub, caching, Lua scripting	→ Redis
Networking	TCP/IP, DNS, TLS, HTTP/2, gRPC	→ Networking
Security	Auth flows, JWT, OAuth2, encryption, OWASP	→ Security
DevOps	Docker, Kubernetes, CI/CD pipelines	→ DevOps
Git	Branching, rebase, cherry-pick, worktrees	→ Git

Interview Self-Check

Before your interview, confirm you can answer:

1. Explain your design with at least one alternative considered
2. What breaks first at 10× traffic?
3. How do you detect and recover from failures?
4. How does your solution behave under partial failure or network partition?

Interview Success Formula

Good answers connect three layers: Concept (what it is) → Design choice (when to use it, trade-offs) → Operations (how it behaves at scale or under failure).

Common Interview Traps

• Definition-only answers without trade-off reasoning
• Ignoring scale assumptions (QPS, payload size, latency targets)
• Treating consistency, reliability, and cost as independent concerns
• Forgetting operational details: monitoring, alerting, rollback strategy

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📊 DSA Coding Training 20-Week Roadmap

A structured 20-week curriculum for mastering coding interview patterns. Each week focuses on one core pattern with progressive difficulty.

Week	Pattern	Key Topics	Weekly Guide
1	Arrays & Prefix Sums	Two-sum, subarray sums, running totals	→ Week 1
2	Two Pointers & Sliding Window	Container with most water, substring problems	→ Week 2
3	Linked Lists & Pointers	Reversal, cycle detection, merge	→ Week 3
4	Hash Tables & Sets	Frequency counting, anagrams, grouping	→ Week 4
5	Stacks, Queues & Monotonic	Valid parentheses, next greater element	→ Week 5
6	Binary Trees & BST	DFS/BFS traversal, LCA, BST operations	→ Week 6
7	Graph Foundations	BFS, DFS, adjacency list, connected components	→ Week 7
8	Advanced Graphs	Topological sort, cycle detection, Dijkstra	→ Week 8
9	Binary Search	Search space reduction, rotated arrays	→ Week 9
10	Recursion & Backtracking	Permutations, combinations, N-Queens	→ Week 10
11	Intervals & Sweep Line	Merge intervals, meeting rooms	→ Week 11
12	Heaps & Greedy	K-largest elements, task scheduling	→ Week 12
13	Dynamic Programming 1D	Fibonacci variants, house robber, DP on strings	→ Week 13
14	Dynamic Programming 2D	Grid DP, edit distance, LCS	→ Week 14
15	Advanced Sliding Window	Variable-size windows, multi-condition problems	→ Week 15
16	Tries & Prefix Trees	Word search, autocomplete, prefix matching	→ Week 16
17	Shortest Paths & MST	Dijkstra, Bellman-Ford, Prim, Kruskal	→ Week 17
18	Disjoint Set Union	Union-find, Kruskal, dynamic connectivity	→ Week 18
19	Bit Manipulation & Math	XOR tricks, power of two, prime sieve	→ Week 19
20	Comprehensive Review	Mock interviews, system + coding integration	→ Week 20

Start Here

New to DSA training? Read the 20-Week Roadmap Introduction for the full curriculum structure, weekly study plan, and tips for maximizing retention.

DSA Pattern Quick Reference

Pattern	Use When	Typical Complexity
Sliding Window	Fixed/variable window over array/string	O(n)
Two Pointers	Sorted array, in-place manipulation	O(n)
Binary Search	Sorted/monotonic search space	O(log n)
BFS	Shortest path in unweighted graph, level traversal	O(V+E)
DFS + Backtrack	Permutations, combinations, constraint satisfaction	O(n!)
DP 1D	Overlapping subproblems, 1D state	O(n)
DP 2D	Grid problems, string comparison	O(m×n)
Heap	K-th element, streaming median	O(n log k)
Union-Find	Dynamic connectivity, cycle detection in graphs	O(α(n)) ≈ O(1)
Trie	Prefix matching, word search	O(L) per operation

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📚 Engineering Books

Distilled notes and key takeaways from essential software engineering books.

Interview Preparation Track

Book	Author	Focus	Notes
Cracking the Coding Interview	Gayle McDowell	Data structures, algorithms, system design, OOP, concurrency	→ Notes
System Design Interview Vol.1	Alex Xu	4-step framework + 10 real system designs (URL shortener, Twitter, etc.)	→ Notes
System Design Interview Vol.2	Alex Xu & Sahn Lam	Advanced designs: payments, maps, stock exchange	→ Notes

Software Craft Track

Book	Author	Focus	Notes
Effective Java	Joshua Bloch	90 best practices: generics, lambdas, APIs, concurrency, serialization	→ Notes
Clean Code	Robert C. Martin	Naming, functions, comments, formatting, error handling	→ Notes
Building Microservices	Sam Newman	Service decomposition, resilience, integration, deployment	Coming soon

Deep Foundations Track

Book	Author	Focus	Notes
Designing Data-Intensive Applications (DDIA)	Martin Kleppmann	Storage, replication, partitioning, transactions, distributed systems	→ Notes
Clean Architecture	Robert C. Martin	Architecture principles, dependency rules, component isolation	→ Notes

Reading Order

For interviews: Cracking the Coding Interview → System Design Interview Vol.1 → Vol.2

For engineering depth: Effective Java → Clean Code → Building Microservices → DDIA

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☁️ Cloud Certifications AWS DVA-C02

Targeted preparation for the AWS Certified Developer – Associate (DVA-C02) exam.

Exam Overview

Domain	Weight	Key Services
Domain 1: Development with AWS Services	32%	Lambda, DynamoDB, S3, API Gateway, SQS/SNS
Domain 2: Security	26%	IAM, Cognito, Secrets Manager, KMS, STS
Domain 3: Deployment	24%	CodePipeline, CodeDeploy, Elastic Beanstalk, CloudFormation
Domain 4: Troubleshooting & Optimization	18%	CloudWatch, X-Ray, performance tuning

Study Path

#	Topic	Key Concepts	Link
1	DVA-C02 Roadmap	Full exam roadmap and study strategy	→ Roadmap
2	AWS Overview	Core services, regions, shared responsibility	→ Overview
3	Lambda	Invocation models, cold start, layers, destinations, DLQ	→ Lambda
4	DynamoDB	Keys, GSI/LSI, streams, DAX, single-table design	→ DynamoDB
5	API Gateway	REST vs HTTP API, authorizers, throttling, caching	→ API Gateway
6	S3	Storage classes, lifecycle, encryption, presigned URLs	→ S3
7	IAM	Roles, policies, STS, least privilege patterns	→ IAM
8	Messaging	SQS, SNS, EventBridge, Kinesis — choosing the right service	→ Messaging
9	CloudFormation & SAM	IaC, stack management, SAM for serverless	→ CloudFormation
10	Containers	ECS, ECR, Fargate, App Runner	→ Containers
11	RDS & Aurora	Multi-AZ, read replicas, Aurora Serverless	→ RDS & Aurora
12	ElastiCache	Redis vs Memcached, cache strategies	→ ElastiCache
13	Monitoring	CloudWatch, CloudTrail, X-Ray, Logs Insights	→ Monitoring
14	Security	KMS, Secrets Manager, WAF, Shield	→ Security
15	Serverless Patterns	Event-driven, fan-out, saga patterns	→ Patterns
16	Exam Tips & Traps	Last-minute key facts and common traps	→ Exam Tips
17	Mock Exam	Full practice exam with explanations	→ Mock Exam

DVA-C02 High-Priority Topics

• Lambda — invocation types, cold start optimization, reserved concurrency
• DynamoDB — single-table design, GSI/LSI trade-offs, strongly vs eventually consistent reads
• SQS — visibility timeout, DLQ, long polling, FIFO vs Standard
• IAM — policy evaluation order, role assumption, resource-based vs identity-based policies
• CloudFormation — rollback triggers, change sets, stack drift, cross-stack references

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Who This Is For

• Backend engineers preparing for system design and coding interviews
• Developers studying for the AWS DVA-C02 certification
• Engineers onboarding to new backend or distributed systems domains
• Anyone building a structured, long-term engineering knowledge base