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 →

bluetape4k Projects

bluetape4k-projects

Repository ↗

Core Kotlin libraries for caches, coroutines, data access, infrastructure, and Spring applications.

bluetape4k Projects Projects NearJCache Semantics

Explore L1 hits, L2 fills, conditional writes, bounded bulk policy, epoch-gated clear, and lifecycle boundaries.

Open visual companion → bluetape4k Projects Projects NetCDF CF Import & Progress

Play CF coordinate resolution, bounded two-pass writes, slice checkpoints, timeout cleanup, and explicit retry ownership.

Open visual companion → bluetape4k Projects Projects NetCDF Data Model

Explore how one self-describing NetCDF container becomes series, fields, volumes, and domain-specific products across weather, ocean, satellite, environment, and geoscience.

Open visual companion → bluetape4k Projects Projects NATS JetStream Flow

Play the cold Flow<Message> bridge from pull and push consumers through bounded delivery, caller-owned ack/nak/term, redelivery, drop, cancellation, and completion.

Open visual companion → bluetape4k Projects Projects Coroutines Flow Operator Marble Explorer

Select and replay 66 reactive Flow operators across transform, admission, time, combine, async, and error families on a shared marble timeline.

Open visual companion → bluetape4k Projects Projects Tenant Context Carriers

Compare ThreadLocal, ScopedValue, Reactor Context, and Ktor ApplicationCall tenant carriers across lexical scopes, reactive subscriptions, and dispatcher boundaries.

Open visual companion →

bluetape4k AWS

bluetape4k-aws

Repository ↗

Coroutine-friendly AWS SDK adapters with explicit batching, ordering, checkpoint, cancellation, and caller-owned policy boundaries.

bluetape4k AWS AWS SQS Batch Reliability

Play normal delivery, partial handler failure, delete failure, cancellation, and observation failure in one bounded batch lifecycle.

Open visual companion → bluetape4k AWS AWS Streams Shard Consumer Lab

Compare Kinesis and DynamoDB Streams discovery, graph ordering, bounded concurrency, emit-then-checkpoint, and failure boundaries.

Open visual companion → bluetape4k AWS Spring Modulith event externalization

Trace outbound SNS/SQS publishers and inbound DIRECT-body or SNS-wrapped-SQS-body envelopes through version validation, idempotency, dispatch, and acknowledgement boundaries.

Open visual companion → bluetape4k AWS AWS SNS signature verification

Trace structural parsing, exact TopicArn allowlisting, certificate retrieval and caching, SignatureVersion 1/2 verification, and fail-closed handler admission.

Open visual companion → bluetape4k AWS AWS SQS Extended Client lifecycle

Trace inline and S3-offloaded payloads through signed pointers, bounded restore, handler completion, SQS acknowledgement, and retryable cleanup.

Open visual companion →

bluetape4k Image

bluetape4k-image

Repository ↗

Image processing and intelligence APIs that separate decoding, detection facts, policy decisions, and privacy-safe snapshots.

bluetape4k Image Image Intelligence Policy and Privacy

Step through qualification, parallel analysis, fail-closed policy, and application-owned privacy side effects.

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