#System design

Last updated    - V8 (19-Jan-2026)

Key Concepts

S.No	Topic	Sub-Topics
1	System Design	Functional vs Non-Functional Requirements, Scalability, Availability & Reliability, Latency & Throughput, CAP Theorem, Consistency Models, Trade-offs
2	Requirements & Capacity Estimation	Functional Requirements, Non-Functional Requirements, QPS Estimation, Storage Estimation, Bandwidth Estimation, Traffic Estimation, Back-of-the-Envelope Calculations
3	API & Interface Design	REST APIs, gRPC, API Versioning, Idempotency, Authentication & Authorization, Rate Limiting, Request Validation
4	Networking	HTTP/HTTPS, DNS, TCP/IP, Load Balancers, CDN, Firewall & NAT, Timeouts & Keep-Alive
5	High-Level Design (HLD)	Component Diagram, Data Flow Diagram, Service Boundaries, Microservices, Database Selection, Scalability, Bottleneck Identification
6	Low-Level Design (LLD)	SOLID Principles, Design Patterns, Class Diagrams, Sequence Diagrams, Object-Oriented Design, API & Component Design, Extensibility
7	Databases	SQL vs NoSQL, Indexing, Normalization, Sharding, Replication, Partitioning, ACID vs BASE
8	Caching	Why Caching, Cache-Aside, Write-Through, Write-Behind, TTL, LRU/LFU, Cache Invalidation
9	Scalability	Vertical vs Horizontal Scaling, Auto Scaling, Stateless Services, Service Discovery, Load Balancing, Database Scaling, Partitioning
10	Storage Systems	Object Storage, Block Storage, File Storage, Data Lakes, Log Aggregation, Backup & Recovery, Hot vs Cold Storage
11	Distributed Systems	Consistency Models, Strong vs Eventual Consistency, Distributed Transactions, 2PC/3PC, Saga Pattern, Consensus, Leader Election
12	Messaging & Event-Driven Systems	Kafka, RabbitMQ, SQS, Pub/Sub, Event Streaming, Sync vs Async Communication, Delivery Semantics
13	Fault Tolerance & Resilience	Retry, Timeout, Circuit Breaker, Bulkhead, Rate Limiting, Failover, Graceful Degradation
14	Security	OAuth 2.0, JWT, RBAC/ACL, TLS/SSL, Encryption at Rest & In Transit, Secrets Management, OWASP Basics
15	Observability	Logging, Metrics, Distributed Tracing, Monitoring, Alerting, SLI/SLO/SLA, Dashboards
16	DevOps & Deployment	CI/CD, Docker, Kubernetes, Blue-Green Deployment, Canary Deployment, Infrastructure as Code, GitOps
17	Social Media System Design	Feed Generation, Fan-out, Timeline Service, Follow Graph, Caching, Sharding, Real-time Notifications
18	E-Commerce System Design	Product Catalog, Cart, Order Service, Inventory, Payment, Search, Event-Driven Architecture
19	Ride-Hailing System Design	Geospatial Queries, Location Tracking, Driver Matching, Trip Management, Real-time Events, Surge Pricing, Scalability
20	Video Streaming System Design	Video Upload, Transcoding, Object Storage, CDN, Metadata, Streaming, Content Delivery
21	Banking & Payment System Design	Payment Gateway, Transaction Processing, Ledger, Idempotency, Fraud Detection, Distributed Transactions, Disaster Recovery

#Microservice

Last updated    - V7 (19-Jan-2026)

Key Concepts

#	Microservices Concept	Description	Pattern
1	Microservice	Small, independently deployable business service	Decomposition Pattern
2	Service Decomposition	Break application into smaller business services	Decompose by Business Capability
3	API Gateway	Single entry point for client requests	API Gateway Pattern
4	Service Discovery	Dynamically finds available service instances	Service Discovery Pattern
5	Load Balancing	Distributes requests across service instances	Load Balancer Pattern
6	Service Communication	Enables communication between services	Remote Procedure Call Pattern
7	Asynchronous Communication	Services communicate without waiting for response	Messaging Pattern
8	Event-Driven Architecture	Services communicate through business events	Event-Driven Pattern
9	Database per Service	Each service owns its data	Database-per-Service Pattern
10	Shared Database	Multiple services share a database	Shared Database Pattern
11	Distributed Transaction	Transaction spans multiple services	Distributed Transaction Pattern
12	Saga	Manages transactions across multiple services	Saga Pattern
13	Saga Choreography	Services coordinate through events	Choreography Pattern
14	Saga Orchestration	Central coordinator manages the workflow	Orchestration Pattern
15	Circuit Breaker	Prevents repeated calls to failing services	Circuit Breaker Pattern
16	Retry	Reattempts failed operations	Retry Pattern
17	Timeout	Stops calls that take too long	Timeout Pattern
18	Bulkhead	Isolates failures between services	Bulkhead Pattern
19	Fallback	Provides alternative behavior when a service fails	Fallback Pattern
20	Rate Limiting	Controls the number of incoming requests	Rate Limiting Pattern
21	Caching	Stores frequently accessed data for faster retrieval	Cache-Aside Pattern
22	CQRS	Separates read and write operations	CQRS Pattern
23	Event Sourcing	Stores state changes as a sequence of events	Event Sourcing Pattern
24	Idempotency	Ensures repeated requests don't create duplicate effects	Idempotency Pattern
25	Strangler Fig	Gradually replaces a legacy application	Strangler Fig Pattern
26	Anti-Corruption Layer	Protects a new service from legacy models	Anti-Corruption Layer Pattern
27	Backend for Frontend	Provides a dedicated backend for each client	BFF Pattern
28	Aggregator	Combines responses from multiple services	Aggregator Pattern
29	Adapter	Converts one interface into another	Adapter Pattern
30	Sidecar	Runs supporting functionality alongside a service	Sidecar Pattern
31	Service Mesh	Manages service-to-service communication	Service Mesh Pattern
32	Ambassador	Handles external communication through a proxy	Ambassador Pattern
33	Externalized Configuration	Keeps configuration outside application code	External Configuration Pattern
34	Centralized Configuration	Provides configuration from a central location	Configuration Server Pattern
35	Health Check	Determines whether a service is operational	Health Check Pattern
36	Distributed Tracing	Tracks requests across multiple services	Distributed Tracing Pattern
37	Centralized Logging	Collects logs from multiple services	Centralized Logging Pattern
38	Observability	Provides visibility into distributed system behavior	Observability Pattern
39	Contract Testing	Validates compatibility between service consumers and providers	Consumer-Driven Contract Pattern
40	API Versioning	Allows APIs to evolve without breaking clients	API Versioning Pattern
41	Authentication	Verifies the identity of users or services	Authentication Pattern
42	Authorization	Controls access to resources	Authorization Pattern
43	Token Propagation	Passes user/service identity between services	Token Propagation Pattern
44	Zero Trust	Services are not automatically trusted	Zero Trust Pattern
45	Blue-Green Deployment	Uses two environments for safer releases	Blue-Green Pattern
46	Canary Deployment	Releases changes gradually	Canary Release Pattern
47	Rolling Deployment	Gradually replaces old service instances	Rolling Update Pattern
48	Horizontal Scaling	Adds additional service instances	Scale-Out Pattern
49	Fault Isolation	Prevents one service failure from spreading	Failure Isolation Pattern
50	Independent Deployment	Allows services to be deployed separately	Independent Deployment Pattern

Interview question

What are Microservices, and how do they differ from Monolithic architecture?

Why are Microservices important for AI and Agentic AI platforms?

What are the core principles of Microservices architecture?

What are the advantages and disadvantages of Microservices?

How do you identify service boundaries in a Microservices architecture?

What is Domain-Driven Design (DDD), and how does it help Microservices?

What is a bounded context in Microservices?

How do you decompose a monolithic application into Microservices?

What are the common communication patterns between Microservices?

How do synchronous and asynchronous communication differ in Microservices?

What is REST-based communication in Microservices?

What is gRPC, and when would you use it in Microservices?

What is event-driven architecture in Microservices?

How do Kafka and Microservices work together in AI systems?

What is an API Gateway, and why is it needed in Microservices?

How do API Gateways support AI and LLM-based applications?

What is service discovery, and how does it work?

How do Eureka, Consul, and Kubernetes Service Discovery differ?

What is client-side vs server-side service discovery?

How do Microservices handle dynamic scaling?

What is centralized configuration management in Microservices?

How does Spring Cloud Config help Microservices?

What is distributed tracing, and why is it important?

How do OpenTelemetry and Zipkin help Microservices observability?

What metrics should be monitored in Microservices?

How do logs, metrics, and traces work together?

What is the role of Prometheus and Grafana in Microservices?

How do you monitor AI service latency in Microservices?

What is resiliency in Microservices?

How do Circuit Breakers work in Microservices?

How does Resilience4j improve fault tolerance?

What are retries, bulkheads, and rate limiters?

How do you prevent cascading failures in Microservices?

How do you design highly available Microservices?

What is eventual consistency in Microservices?

How do SAGA patterns work in distributed transactions?

What is choreography vs orchestration in SAGA?

How do Microservices manage distributed data?

Why should each Microservice own its database?

How do you implement CQRS in Microservices?

What is Event Sourcing, and when should it be used?

How do Microservices support AI data pipelines?

How do Microservices integrate with Vector Databases?

How do Microservices integrate with RAG architectures?

What is an AI Gateway in an LLM platform?

How do you design a Chatbot using Microservices?

How do you design an Agentic AI platform using Microservices?

What Microservices are typically required in an AI platform?

How do Prompt Services fit into a Microservices architecture?

How do Memory Services fit into an Agentic AI architecture?

How do Tool Services fit into Agentic AI platforms?

How do RAG Services fit into AI architectures?

How do Model Routing Services work in AI platforms?

How do Guardrail Services improve AI safety?

How do Evaluation Services measure AI quality?

How do AI Observability Services work?

How do Microservices integrate with OpenAI APIs?

How do Microservices integrate with Azure OpenAI?

How do you manage multiple LLM providers in Microservices?

How do you implement model fallback strategies?

How do you implement AI cost optimization in Microservices?

How do you track token consumption across services?

How do Redis and Microservices work together?

How does Elasticsearch support Microservices?

How does PostgreSQL support Microservices?

How do MongoDB and Microservices work together?

How do Docker and Microservices work together?

How does Kubernetes manage Microservices?

What are Kubernetes Deployments, Services, and Ingress?

How does Horizontal Pod Autoscaling work?

How do Microservices support multi-region deployments?

How do you secure Microservices using OAuth2?

How do JWT tokens work in Microservices?

How do API Gateways enforce security?

How do you implement zero-trust security in Microservices?

How do service-to-service authentication mechanisms work?

How do you secure AI tools exposed through Microservices?

How do you prevent prompt injection from propagating across services?

How do you protect sensitive data in AI Microservices?

How do you implement PII masking across Microservices?

How do you test Microservices independently?

How do contract tests work in Microservices?

How do integration tests work across Microservices?

How do you mock dependent services during testing?

How do you perform performance testing in Microservices?

How do you perform chaos engineering in Microservices?

How do CI/CD pipelines support Microservices?

How do GitOps practices improve Microservices deployments?

How do Blue-Green deployments work?

How do Canary deployments work?

How do Feature Flags help Microservices releases?

How do you troubleshoot production issues in Microservices?

How do you optimize latency in distributed Microservices?

How do you handle high-throughput event processing?

How do you design a scalable enterprise AI platform using Microservices?

How would you design a production-grade RAG platform using Microservices?

How would you design a multi-agent AI platform using Microservices?

How would you design a global-scale AI and LLM platform using Microservices?

Related Topics

#DSA

Last updated    - V7 (19-Dec-2025)

Key Concepts

S.No	Topic	Sub-Topics
1	Introduction & Complexity	What is DSA, Time Complexity (Big-O), Space Complexity, Best/Average/Worst case, Simple examples
2	Arrays Basics	Declaration & Access, Common operations, Two-pointer technique, Sliding window intro, In-place vs extra space
3	Arrays Problems	Subarray sum, Prefix sums, Kadane's algorithm, Rearrange problems, Dutch National Flag
4	Strings Basics	Immutability, Common operations, Character arrays, String builders, Unicode & encodings
5	Strings Algorithms	Pattern search (KMP), Rabin-Karp, Anagrams, Palindromes, Trie intro
6	Linked Lists	Singly vs Doubly, Operations (insert/delete), Reverse list, Fast/Slow pointers, Detect cycle
7	Stacks & Queues	LIFO vs FIFO, Implementation using arrays/linked list, Monotonic stack, Circular queue, Applications
8	Recursion & Backtracking	Recurrence relations, Call stack, Backtracking patterns, Subset/permutation generation, N-Queens
9	Sorting Algorithms	Bubble, Selection, Insertion, Merge sort, Quick sort
10	Searching Algorithms	Linear search, Binary search, Binary search on answer, Search in rotated array, Interpolation search
11	Hashing & Hash Tables	Hash functions, Collision resolution, HashMap/HashSet, Frequency maps, Anagram/counting problems
12	Priority Queue & Heaps	Binary heap, Insert/extract, Heapify, Kth largest, Heap for merge/k-way
13	Trees Basics	Binary tree, Tree traversal (pre/in/post), Height/depth, Recursive vs iterative, Tree representations
14	Binary Search Tree (BST)	BST properties, Insert/Delete/Search, Lowest common ancestor, Range queries, Balanced vs unbalanced
15	Tries (Prefix Trees)	Insert/Search, Prefix queries, Autocomplete, Word dictionary, Memory considerations
16	Graphs Basics	Directed vs undirected, Adjacency list/matrix, Graph traversal, Connected components, Dense vs sparse
17	Graph Traversal	BFS, DFS, Tree vs graph traversal, Level order, Parent/Distance tracking
18	Shortest Path Algorithms	Dijkstra, Bellman-Ford, SPFA, Weighted vs unweighted, Single-source vs all-pairs
19	Minimum Spanning Tree	Kruskal, Prim, Union-Find intro, Cycle detection, Applications
20	Union-Find / Disjoint Set	Make/Find/Union, Path compression, Union by rank, Connected components, Offline queries
21	Dynamic Programming	Overlapping subproblems, Optimal substructure, Memoization vs tabulation, State definition, Simple examples
22	Common DP Patterns	0/1 Knapsack, Unbounded knapsack, Longest Increasing Subsequence, Longest Common Subsequence, DP on strings
23	Advanced DP	Bitmask DP, DP on trees, Digit DP, Convex hull trick intro, Optimization techniques
24	Greedy Algorithms	Greedy choice property, Activity selection, Huffman coding, Fractional knapsack, Interval scheduling
25	Bit Manipulation	Bit ops (&,|,^,~,<<,>>), Count bits, Lowbit, Bitmask tricks, XOR properties
26	Sliding Window & Two Pointers	Fixed window, Variable window, Two-pointer for pairs, Subarray problems, Window optimization
27	Prefix/Suffix & Difference Arrays	Prefix sums, Suffix sums, Prefix max/min, Range update via diff array, Prefix product
28	Segment Tree & Fenwick Tree	Point update & range query, Range update & point query, Lazy propagation, Fenwick implementation, Use-cases
29	Advanced Graphs & Flows	Topological sort, DAG applications, Max flow (Edmonds-Karp), Min-cut, Matching basics
30	Interview Prep & Practice	Common patterns, Problem-solving checklist, Mock interviews, Platforms (LeetCode, Codeforces), Time-boxed practice

Interview question

Basic Level

1. What is an algorithm?
2. Explain Time Complexity and Big-O notation.
3. What is Space Complexity?
4. What is an Array?
5. Difference between Array and Linked List?
6. What is a Linked List? Types?
7. What is a Stack? Explain operations.
8. What is a Queue? Explain types.
9. Explain postfix, prefix, infix notations.
10. What is a Hash table?
11. What is a Tree data structure?
12. Difference between Binary Tree and Binary Search Tree (BST)?
13. What is a Graph?
14. Difference between DFS and BFS.
15. What is Recursion?
16. What is Divide and Conquer approach?
17. Explain Bubble Sort algorithm.
18. Explain Selection Sort algorithm.
19. Explain Insertion Sort algorithm.
20. What is Linear Search?
21. What is Binary Search?
22. What is Dynamic Programming (basic definition)?
23. What is Greedy Algorithm?
24. What is a Heap?
25. What is a Hash collision?

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Intermediate Level

1. Explain Merge Sort algorithm and its complexity.
2. Explain Quick Sort and its complexity.
3. Explain Two-pointer technique with examples.
4. Explain Sliding Window technique.
5. What is Prefix Sum and where is it used?
6. Explain Kadane?s algorithm.
7. What is a Circular Linked List?
8. How do you detect a cycle in a Linked List?
9. What is a Doubly Linked List?
10. What is a Priority Queue?
11. How do you implement a Queue using Stacks?
12. How do you implement a Stack using Queues?
13. What is a Trie data structure?
14. Difference between Tree and Graph.
15. What is a Balanced Binary Tree?
16. What is AVL Tree?
17. What is Red-Black Tree?
18. Explain Dijkstra?s algorithm.
19. What is Bellman-Ford algorithm?
20. Explain Floyd-Warshall algorithm.
21. What is Kruskal?s algorithm?
22. What is Prim?s algorithm?
23. What is Union-Find data structure?
24. What is Topological Sorting?
25. What is Backtracking? Give example.

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Advanced Level

1. Explain Segment Tree and its operations.
2. What is a Fenwick Tree (Binary Indexed Tree)?
3. Difference between Segment Tree and Fenwick Tree.
4. Solve: Maximum product subarray.
5. Solve: Longest increasing subsequence.
6. Explain Longest Common Subsequence.
7. What is KMP algorithm?
8. Explain Rabin-Karp algorithm.
9. Explain the concept of rolling hash.
10. What is a Min-Cut and Max-Flow problem?
11. Explain Edmonds-Karp Algorithm.
12. Explain Kahn?s algorithm.
13. Explain A* search algorithm.
14. What is NP, NP-hard, and NP-complete?
15. Explain Traveling Salesman Problem.
16. Explain Bitmask DP with example.
17. Explain DP on trees.
18. Explain DP on graphs.
19. How does binary lifting work?
20. What is a Sparse Table?
21. Explain Lowest Common Ancestor problem.
22. Implement LRU Cache logic.
23. What is a Bloom Filter?
24. Explain Consistent Hashing.
25. Explain Suffix array and Suffix tree.

---

Expert Level

1. Solve: Maximum subarray sum for circular array.
2. Solve: Median of two sorted arrays (log approach).
3. Solve: Find Kth smallest element in sorted matrix.
4. Solve: Word ladder shortest path.
5. Solve: N-Queens problem optimized solution.
6. Solve: Shortest path in a maze using BFS.
7. Solve: Course schedule (detect cycle in graph).
8. Solve: Clone graph problem.
9. Solve: Regular expression matching (DP).
10. Solve: Edit distance problem (DP).
11. Solve: Palindromic subsequence count (DP).
12. Solve: Max rectangle in binary matrix.
13. Solve: Largest histogram rectangle.
14. Solve: Minimum window substring problem.
15. Solve: Coin change problem variants.
16. Solve: Sliding window maximum problem.
17. Solve: Find bridges and articulation points.
18. Solve: Euler path/circuit check.
19. Solve: Detect negative cycle in graph.
20. Solve: Longest path in DAG.
21. Solve: Kth smallest element using order-statistic tree.
22. Solve: Streaming median problem.
23. Solve: Top K frequent elements problem.
24. Solve: Find strongly connected components (Kosaraju).
25. Solve: Implement efficient autocomplete system using Trie.

Related Topics