Senior Native Developer (iOS & Android)

The second volume of Grokking the System Design Interview, aimed at senior and staff (L5/L6) design rounds. It works through harder case studies such as a payment system, flash sale, notification service, unique ID generator, Gmail, Reddit, Google Calendar and a code judging system, then goes beneath them with patterns like quorum, write-ahead logs and vector clocks and deep dives into Dynamo, Cassandra, Kafka, Chubby, HDFS, GFS and BigTable.

• System design
• Backend
• Job search

The original Grokking system design course, which made the design round learnable. It teaches a repeatable interview approach and the key trade-offs (SQL versus NoSQL, strong versus eventual consistency, REST versus RPC and more), then works through 15 classic designs such as a URL shortener, Instagram, Dropbox, Twitter, YouTube, a rate limiter, a web crawler, Uber and Ticketmaster, each with requirements, estimates and trade-off discussion.

• System design
• Job search
• Backend

A course on object oriented and low level design interviews. It teaches a repeatable method (requirements, actors and use cases, class diagram, code) with UML basics and SOLID, then applies it to 22 case studies such as a parking lot, elevator, ATM, chess, movie booking, Splitwise and an in-memory cache, with runnable code in Python, Java and C++. It suits candidates facing a dedicated OOD or LLD round.

• Job search
• System design
• CS fundamentals

A text based course on the classic object oriented design patterns, 22 in all across creational, structural and behavioural groups, with a real world problem, class diagram, pros and cons and code in Python, Java, JavaScript and C++ for each. It suits developers who meet patterns in code reviews and want to apply them where they help rather than everywhere, and those preparing for low level design discussions.

• System design
• CS fundamentals
• Backend

A popular English channel for native Android development with Kotlin: Jetpack Compose, Kotlin Flows, MVVM architecture, testing, storage, security, Kotlin Multiplatform and Spring Boot with Kotlin. Philipp explains why code works, not just how. It suits Android learners past the basics and Kotlin developers who want production-quality habits.

• Web
• Mobile
• Testing
• Backend

A quick-revision companion to the Sefism mobile roadmap, from your platform language to shipping in the stores: language essentials, UI and layout, state and navigation, networking and local data, device features and notifications, testing, performance and accessibility, and publishing and releases. It comes in Flutter, React Native, Android (Kotlin and Compose) and iOS (Swift and SwiftUI) editions, each concept with a short snippet and the classic mistake. Read a chapter to refresh a stage, or jump to one concept when you need it.

• Web
• Mobile
• Testing