25 real production scenarios for experienced Java and Spring Boot developers: OOM, high CPU, deadlocks, N+1, @Transactional traps, duplicate payments, with tools, fixes and runnable code.
Hashing, bucket index, collisions, treeify at 8 and 64, load factor and resize, explained with diagrams and programs run on JDK 25, plus 12 interview questions.
40 Java Stream API coding interview questions with solutions and real JDK 25 output: duplicates, second highest salary, groupingBy, first non-repeated character, toMap gotchas.
50 Java coding interview programs on strings, numbers, arrays, collections, linked lists and threads, each run on JDK 25 with real output, complexity and a follow-up.
A repeatable 45-minute system design interview framework with timings and phrases, the core concepts, an estimation cheat sheet and 15 practice problems with key ideas.
Design a URL shortener like an interview answer: estimates, API, database, base62 short codes vs hashing, 301 vs 302 redirects, caching, sharding and abuse prevention.
A 6-step approach to LLD and machine coding rounds, SOLID and the six patterns that matter, plus a parking lot, LRU cache and Splitwise worked out in runnable Java 25.
15 DSA patterns with the signal words that give each away, a tested Java template, its complexity, LeetCode problems to practice, and an 8-week placement plan.
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