Examples

Workshop Repositories

Backend examplesbluetape4k-workshopGeneral backend examples for bluetape4k libraries, including Spring, Kotlin patterns, virtual threads, observability, Gatling, and production-style application flows.Exposed JDBC examplesexposed-workshopLearning material for JetBrains Exposed ORM. Covers SQL DSL, DAO, Spring Boot, Ktor, transactions, migrations, repository patterns, and progressive workshop chapters.Exposed R2DBC examplesexposed-r2dbc-workshopReactive and coroutine-oriented Exposed R2DBC examples with H2, PostgreSQL, MySQL, MariaDB, repositories, Spring WebFlux, Gatling, and migration-focused samples.Optimization examplestimefold-workshopTimefold Solver workshop examples for planning, scheduling, and optimization problems. Useful for understanding solver-driven backend workflows.Reference applicationclinic-appointmentA clinic appointment scheduling system built with Kotlin, Spring Boot 4, Exposed ORM, Flyway, Timefold, frontend integration, and realistic application boundaries.

Representative Designs

Start with these visual companions when the source example spans several business rules, consistency boundaries, or recovery paths. Each companion connects the scenario and design decisions to the implemented structure and an executable path.

Clinic appointment

clinic-appointment

Repository ↗

Reference application designs for product composition, scheduling policies, appointment plans, and capacity management.

Clinic appointment Appointment Plan and Capacity

See how appointment plans, slot generation, capacity changes, and booking decisions remain consistent.

Open visual companion → Clinic appointment Scheduling Policy Foundation

Follow the scheduling policy model from source rules to validation, conflicts, and operational changes.

Open visual companion → Clinic appointment Profile Change Reservation Reevaluation

Trace a minimal profile-change event through fair dispatch, state decisions, and privacy-safe recovery for in-progress reservations.

Open visual companion → Clinic appointment Product Scheduling Classification

Classify product traits, separate product duration from clinic capacity, and inspect the validated booking contract.

Open visual companion → Clinic appointment Package Product Composition

Compare repeated, composite, and choose-M-of-N packages while preserving item-level time, resources, and dependencies.

Open visual companion → Clinic appointment Execution BOM to Appointment Flow

Follow an immutable execution BOM through plan revisions, visit candidates, proposals, consent, and confirmed resource allocation.

Open visual companion →

bluetape4k workshop

bluetape4k-workshop

Repository ↗

Complex example applications that connect domain decisions with event sourcing, concurrency control, payment, inventory, leader election, and recovery.

bluetape4k workshop Event-sourced Promotion Voucher Campaign

Trace voucher issuance and redemption through commands, immutable events, projections, and recovery.

Open visual companion → bluetape4k workshop Concert Ticket Flash Sale

Follow inventory, payment, refund, and ticket processing until the purchase reaches a consistent outcome.

Open visual companion → bluetape4k workshop Kafka Outbox Fallback

Compare how direct Kafka publication, timeout ambiguity, fallback persistence, relay recovery, and dead-letter handling change API, database, and event states.

Open visual companion → bluetape4k workshop Leader Job Safety Lab

Compare lease overruns, network partitions, mixed-version rollouts, and non-fenceable effects to see where fencing tokens and idempotency stop stale work.

Open visual companion →

Exposed workshop

exposed-workshop

Repository ↗

Runnable examples of cache strategies built with Exposed and Redis, plus DDD boundaries verified with Spring Modulith.

Exposed workshop Exposed and Redis Cache Strategies

Compare cache reads, updates, invalidation, and deferred database persistence across the local cache, Redis, and Exposed.

Open visual companion → Exposed workshop DDD Modulith Boundaries

See how orders and shipping own separate persistence and communicate only through a published event contract.

Open visual companion →

bluetape4k leader

bluetape4k-leader

Repository ↗

Distributed leader election with Redis/Lettuce locks, leases, takeover, bounded group capacity, and Spring Boot integration.

bluetape4k leader LeaderElector Lock and Lease

Follow one Redis-backed leader through lock acquisition, token ownership, lease expiry, takeover, auto-extension, and Spring interception.

Open visual companion → bluetape4k leader LeaderGroupElector Slot Capacity

See how single-leader election expands to N lease-backed slots, including capacity, saturation, expiry, and later admission.

Open visual companion →

bluetape4k Exposed

bluetape4k-exposed

Repository ↗

JetBrains Exposed extensions that make JDBC and R2DBC transaction ownership, repository boundaries, and framework integration explicit.

bluetape4k Exposed JPA to Exposed: Make Transaction Ownership Visible

Compare JPA/Hibernate with Exposed, then trace caller-owned JDBC and coroutine R2DBC transaction boundaries across single- and multi-repository flows.

Open visual companion → bluetape4k Exposed Spring Boot Exposed Activation

Explore the Spring Boot conditions that activate JDBC and R2DBC Exposed mappings, and the application-owned resources each path still requires.

Open visual companion →

Choose By Interest

Interest	Start with	Then compare with
General backend service shape	bluetape4k-workshop	clinic-appointment
Spring Boot service examples	bluetape4k-workshop	exposed-workshop
Ktor service examples	exposed-workshop	exposed-r2dbc-workshop
Exposed JDBC persistence	exposed-workshop	clinic-appointment
Exposed R2DBC and reactive persistence	exposed-r2dbc-workshop	bluetape4k-workshop
Scheduling and optimization	timefold-workshop	clinic-appointment
Full reference application boundaries	clinic-appointment	bluetape4k-workshop