Junior Oracle DBA

A SQL course for interviews that reviews the basics, order of execution, functions, subqueries, joins, set operations, DDL and DML, then works through 69 interview problems graded easy to hard plus 14 unguided test problems, run against a live database in the browser. It suits backend, data and analytics candidates whose SQL stops at a simple inner join, or who need a fast refresher before a SQL round.

• Job search
• Databases
• Backend

A text-based course on how databases work underneath: storage and page layout, indexing, transactions and ACID, concurrency control, partitioning and sharding, replication and consistency, consensus and leader election, recovery, and the main NoSQL families. It ends with case studies designing the databases behind Quora, TikTok, Airbnb and Snapchat. It suits engineers who want their database choices in system design answers to be defensible rather than hand-waved.

• System design
• Databases
• Backend
• Job search

A beginner friendly, text based course on relational database design: data modelling, entity relationship diagrams, keys and integrity constraints, functional dependencies and normalisation up to BCNF and beyond. It finishes with nine case studies, from hospital and bank systems to an Instagram style app, e-commerce and ticket booking. For developers and students who want to design schemas that stay pleasant to work with years later.

• Web
• Databases
• System design
• Backend

A browsable practice library of coding problems that can be filtered by pattern, data structure, difficulty and company, so you can drill exactly the weakness you found this week. Patterns include two pointers, sliding window, hash maps, stacks, backtracking and greedy algorithms, with company filters for Google, Meta, Microsoft, Amazon, Oracle and LinkedIn. Free to browse, with an in-browser editor and solutions.

• Job search
• DSA

A very large site of articles on data structures, algorithms and core CS subjects such as operating systems, DBMS, computer networks and OOP, usually with code in several languages, plus practice problems and paid courses. It is handy for revising a university topic or finding a worked example of a specific algorithm. Quality varies because much is community written, so cross-check anything surprising against a textbook or official documentation.

• DSA
• CS fundamentals
• Databases

MongoDB's official guide to PyMongo, the Python driver, covering connections, CRUD, aggregation, indexes, transactions and the async API that has replaced Motor. Short, practical pages with runnable examples, and the right starting point for any Python backend, script or data pipeline on MongoDB.

• Web
• Databases
• Backend
• Programming