The recall rounds: OS · Networks · DBMS

Learn the concepts

Interview-grade explainers with interactive visualizers — scheduling Gantt charts, a subnet calculator, the TCP handshake, a B+ tree, isolation-level anomalies, and more. The first article in each subject is free.

Processes & threads, scheduling, deadlock, paging, virtual memory, file I/O.

• 01Processes, Threads, and Context Switching
  13 min + quiz
• 02CPU Scheduling: FCFS, SJF, SRTF, Round Robin, and Priority
  15 min + quiz
• 03Concurrency: Race Conditions, Synchronization, and Deadlock
  15 min + quiz
• 04Memory Management: Paging, Segmentation, and Page Replacement
  15 min + quiz
• 05Virtual Memory: Demand Paging, TLB, and Thrashing
  13 min + quiz
• 06File Systems, Disk Scheduling, and I/O
  12 min + quiz

OSI layers, TCP/UDP, subnetting, DNS · HTTP · TLS, and what happens when you type a URL.

• 01The OSI and TCP/IP Models
  12 min + quiz
• 02TCP vs UDP: Reliability, Flow Control, and Congestion Control
  15 min + quiz
• 03IP Addressing, Subnetting, and Routing
  15 min + quiz
• 04DNS, HTTP/HTTPS, and TLS
  15 min + quiz
• 05What Happens When You Type a URL and Press Enter
  14 min + quiz
• 06Sockets, Load Balancing, and CDNs
  12 min + quiz

Relational SQL, normalization, indexing, transactions & isolation, MVCC, joins.

• 01The Relational Model and SQL Fundamentals
  13 min + quiz
• 02Normalization: From 1NF to BCNF
  14 min + quiz
• 03Indexing and Storage: B+ Trees and Hash Indexes
  15 min + quiz
• 04Transactions, ACID, and Isolation Levels
  15 min + quiz
• 05Concurrency Control: Locking, 2PL, and MVCC
  14 min + quiz
• 06Query Execution: Joins, Plans, and Optimization
  13 min + quiz