PPalabas APIJava field course

Course path

Small quests, real backend artifacts.

Phases stay large enough to tell the engineering story. Quests stay small enough to finish in one focused session.

World 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
Kotlin-to-Java kata committed and tagged phase-0-done.
World 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
All four cinema endpoints proven by curl and Spring context wiring.
World 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
schema-notes.md and time-notes.md explain each invariant with evidence.
World 2Blocked

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
Behavior tests prove what Hibernate does before the article explains it.
World 2Clocked

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
The site can point to a test that proves the fix and the trap.
World 3locked

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
The no-overlap rule survives two concurrent writes on both databases.
World 4locked

API Hardening

DTO boundaries, validation, ProblemDetail, and springdoc.

Estimate
1 weekend
Proof
ArchUnit and error-path tests keep the API honest.
  • DTO boundary
  • Overlap validator
  • ProblemDetail
  • Pagination metadata
  • Swagger
Every error path returns ProblemDetail and no controller exposes entities.
World 5locked

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
Anonymous, USER, ADMIN, expired, and garbage-token cases are all proven.
World 6locked

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
A failed request can be traced from ID to log, status, endpoint, and timing.
World 7locked

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
The live demo proves reads, docs, health, logs, and metrics without fake public writes.
World 8locked

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
Every senior-backend claim has a commit hash or test behind it.