Spring Boot 4.2.0-RC1 and Spring Framework 7.1.0-RC1 are out but not GA. Every 4.2 change that can be run was run against RC1 and 4.1.2: five Kafka keys that 4.1.2 silently ignores, embedded LDAP SSL that now fails without a bundle, @DefaultValue placeholders, the RestTemplate removal warnings and what the properties migrator misses, then an upgrade checklist in order.
What Spring Boot 4.2 changes about OpenTelemetry, run on 4.2.0-RC1 against 4.1.2: meter, tag and span names under the new conventions switch (the documented value fails to start on RC1), one shared OTLP endpoint checked against a local receiver, renamable MDC keys, the long task timer that is off by default, and what to change in dashboards.
Vector search, PostgreSQL tsvector and a Java BM25 fused with Reciprocal Rank Fusion, measured on 60 questions in four kinds: where hybrid search helps, where it hurts, and what it costs at 50,000 rows.
PDF, Word and HTML readers, six chunk sizes, five chunking strategies, metadata in the embedding and idempotent re-ingestion into pgvector, each measured on one fixed set of 37 questions with Spring AI 2.0.2.
A ten-stage Java roadmap for 2026 built on Java 25 and Spring Boot 4.1: what to learn at each stage, how to know you are ready to move on, a visual map, a runnable tour file and links to the matching guides.
A system design interview solved with running code: a URL shortener on Spring Boot 4.1 with base62 codes, block-allocated ids, a Feistel scrambler, Redis cache-aside with negative caching, a Lua token-bucket rate limiter and 24 passing tests.
A low-level design interview solved end to end in Java 25: requirements, entities, Strategy and Observer patterns, lock-free concurrency, real output and 10 passing tests. Full code in the companion repository.
The five SOLID principles in Java 25, each shown as a violating design, the real output that proves it hurts, and the refactored code. Includes a class diagram, one-line interview answers and a runnable file.
Scenario-based Java interview questions for developers with about five years of experience: lost updates, deadlocks, mutable HashMap keys, ThreadLocal leaks, parallel streams, CompletableFuture and production debugging. Eight bugs reproduced in a downloadable Java file with real output, plus 32 answered questions.
50 SQL interview queries with answers for Java developers: Nth highest salary, duplicates, joins, GROUP BY and HAVING, window functions, recursive CTEs and indexes. One sample schema, every query run on PostgreSQL 16 with its real result, plus a downloadable SQL file.