Course path

Small lessons, real backend artifacts.

Modules stay large enough to tell the engineering story. Lessons stay small enough to finish in one focused session.

Module 0published

Java Delta

A Kotlin-to-Java kata that makes Java 25 differences explicit.

Estimate: 2-3 evenings
Proof: A committed kata file with notes on records, Optional, streams, sealed switch, and virtual threads.

Records vs Kotlin data classes
Optional vs nullable types
Streams vs Kotlin collections
Sealed switch vs Kotlin when
Virtual threads are not coroutines

Module 1published

Spring Skeleton

The first Palabas API endpoints under /api/v1.

Estimate: 1 weekend
Proof: A wiring test, curl transcript, ADR-001, and a phase-1-done tag.

Generate the project
First controller
Constructor injection
Service and repository layers
PUT semantics
ADR-001

Module 2Apublished

SQL First

Flyway migrations for the frozen cinema, screen, movie, and showtime model.

Estimate: 1 weekend
Proof: Constraints, EXPLAIN transcripts, schema notes, and time notes.

Cinema schema
Movie and showtime schema
Check constraints
Dedup constraints
Postgres exclusion constraint
Indexes and EXPLAIN

Module 2Bpublished

Hibernate Mental Model

JPA entities mapped after the schema exists.

Estimate: 1 weekend
Proof: Educational tests with annotated SQL logs.

Map the entities
Persistence context
Dirty checking
Lazy boundary failure
Transaction proxy traps
Optimistic locking

Module 2Cpublished

Query Performance

N+1 failures, fixes, and a real geo query.

Estimate: 1 weekend
Proof: Broken and fixed query-count tests plus a stable paginated endpoint.

Cause N+1
Fix with join fetch
Fix with EntityGraph
Fix with DTO projection
Pagination trap
Bounding-box geo query

Module 3published

Invariant Testing + Oracle

Postgres and Oracle lanes that enforce the same domain rules differently.

Estimate: 2 weekends
Proof: Concurrent overlap tests pass on both databases.

Postgres invariant tests
Oracle profile
Vendor Flyway split
Screen row mutex
Concurrent insert race
oracle-notes.md

Module 4published

API Hardening

DTO boundaries, validation, ProblemDetail, and springdoc.

Estimate: 1 weekend
Proof: ArchUnit and error-path tests keep the API honest.

DTO boundary
Domain invariant errors
ProblemDetail
Pagination metadata
Swagger

Module 5published

Security

Bearer-token resource server with ADMIN writes and USER reads.

Estimate: 1 weekend
Proof: Five request outcomes are asserted through the real filter chain.

Resource server
JWT test key
Roles
Method security
CSRF stance

Module 6published

Observability

Operational debugging with logs, metrics, cache behavior, and request IDs.

Estimate: 1 weekend
Proof: Two transcripts reconstruct failures and slow paths from telemetry alone.

Actuator
Prometheus metric
Structured logs
Correlation ID
Cache eviction

Module 7published

Shipping

CI, Docker image, read-only demo profile, and live HTTPS docs.

Estimate: 1 weekend
Proof: Green CI, live Swagger, and v1.0.0 tag.

GitHub Actions
Oracle gate
ARM image
Demo profile
HTTPS

Module 8published

Interview Mapping

A map from canonical interview questions to commits, tests, ADRs, and articles.

Estimate: 2 evenings
Proof: INTERVIEW.md points to concrete artifacts instead of claims.

N+1 story
Transaction story
Concurrency story
Security story
Oracle story

Extraspublished

Supplements

Short operational lessons that keep the local setup and repo practice honest.

Estimate: As needed
Proof: Each supplement turns a real workflow failure into a repeatable project convention.

Java version discipline

Local progress

0 lessons complete

Track

Module 0 / Lesson 0.1

Java 25 for Kotlin Developers

Build the translation table you will use for the rest of the course.

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Module 1 / Lesson 1.1

Generate the Spring Skeleton

Create the smallest Spring Boot app that can carry the rest of the curriculum.

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Module 1 / Lesson 1.3

Constructor Injection and the Wiring Test

Wire controller to service to repository without hiding dependencies.

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Module 1 / Lesson 1.6

ADR-001: Layers and Versioning Stance

Commit the API versioning decision before future endpoints multiply.

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Module 1 / Checkpoint

Phase 1 Boss Fight: Prove the API Skeleton

Finish Phase 1 with tests, curl output, ADR-001, and a tag.

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Module 2A / Lesson 2A.0

Preview: Schema First

See why the database model comes before JPA entities.

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Module 2A / Lesson 2A.1

Cinema and Screen Schema

Create the first Flyway migration for cinemas and screens before any JPA entity exists.

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Module 2A / Lesson 2A.2

Movie and Showtime Schema

Model showtimes as booking facts with stored occupancy windows.

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Module 2A / Lesson 2A.3

Postgres Exclusion Constraint

Enforce no overlapping showtimes per screen with a GiST exclusion constraint.

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Module 2A / Lesson 2A.4

Indexes and EXPLAIN

Add indexes for known reads and capture the planner story without forcing a fake win.

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Module 2A / Checkpoint

Phase 2A Boss Fight: Let SQL Prove It

Finish SQL-first by proving constraints, notes, time handling, ERD, seed data, and EXPLAIN artifacts exist together.

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Module 2B / Lesson 2B.1

Hibernate Mental Model Tests

Map entities after the schema exists and prove Hibernate behavior in labeled tests.

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Module 2C / Lesson 2C.1

N+1, Fetch Strategies, Pagination, and Geo Query

Cause the N+1 problem on purpose, fix it three ways, and show where fetch joins become wrong.

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Module 2C / Checkpoint

Phase 2B/2C Boss Fight: Prove Persistence Performance

Finish the Hibernate and query-performance module with tests, transcripts, and article links.

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Module 3 / Lesson 3.1

Postgres and Oracle Invariants

Open the Oracle lane and keep the no-overlap invariant true without Postgres-only features.

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Module 4 / Lesson 4.1

API Hardening With DTOs and ProblemDetail

Turn the tutorial API into a merge-ready boundary with validation, ProblemDetail, and architecture tests.

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Module 5 / Lesson 5.1

Spring Security Resource Server

Protect writes with a real resource-server filter chain while keeping public reads simple.

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Module 5 / Checkpoint

Phase 5 Checkpoint: Application Readiness

Confirm Phases 0-5 form an application-ready backend story before observability and deployment.

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Module 6 / Lesson 6.1

Observability as a Debugging Story

Add correlation IDs, structured logs, Prometheus metrics, and cache evidence that answer real debugging questions.

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Module 7 / Lesson 7.1

Ship a Read-Only Demo Without Fake Public Writes

Create the CI, image, profile, and runbook for an ARM-hosted read-only Palabas API demo.

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Module 8 / Lesson 8.1

The Interview Map

Map senior-backend interview claims to the exact commits, tests, ADRs, docs, and articles that prove them.

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Module 8 / Checkpoint

Final Checkpoint: Evidence-Backed Java Backend Course

Close M7 with observability, shipping, interview mapping, final articles, and a release/deploy evidence check.

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Extras / Lesson S.1

Supplement: Java Version Discipline

Make the project Java version boring: one local JDK pin, one Gradle toolchain, and one CI provider.