bluetape4k

Kotlin/JVM backend libraries, infrastructure adapters, and workshops held together with just enough blue tape to make distributed systems behave.

What We Build

bluetape4k is a Kotlin-first backend ecosystem for pragmatic server-side development:

coroutine-friendly APIs for blocking, async, and reactive integration points
Spring Boot 3/4 and Java 21/25 era infrastructure modules
persistence, caching, graph, image, text, AWS, audit, and leader-election utilities
real workshop projects that keep examples close to production constraints
tests built around JUnit 5, Testcontainers, Kover, and repeatable Gradle builds

The goal is not to hide complexity. The goal is to give Kotlin developers sharp, well-tested tools for the complexity they actually have.

Repository	What it is for
`bluetape4k-projects`	Core Kotlin/JVM libraries: core utilities, coroutines, data access, infrastructure helpers, Spring Boot support, and virtual-thread-aware components.
`bluetape4k-experimental`	Experimental modules for newer runtime combinations such as Kotlin 2.3, Java 25, Spring Boot 4, and emerging infrastructure patterns.
`bluetape4k-exposed`	JetBrains Exposed extensions for JDBC/R2DBC repositories, cache integration, serialization, and Spring Boot auto-configuration.
`bluetape4k-aws`	AWS SDK v2 and AWS Kotlin SDK helpers with coroutine, Ktor, and Spring Boot integration patterns.
`bluetape4k-image`	Image processing adapters around scrimage and libvips for JVM services that need practical image pipelines.
`bluetape4k-javers`	JaVers audit/diff integration with Redis, Kafka, Exposed, and application event workflows.
`bluetape4k-leader`	Distributed leader election APIs for blocking, async, coroutine, and virtual-thread execution models, with Redis-backed coordination.
`bluetape4k-text`	Korean/Japanese tokenization, language detection, and Aho-Corasick search utilities.
`bluetape4k-graph`	Graph database integrations for Neo4j, Memgraph, Apache AGE, TinkerPop, and FalkorDB.
`bluetape4k-dependencies`	A coordinated BOM for aligning dependency versions across the bluetape4k ecosystem.

Repository	What you can learn from it
`bluetape4k-workshop`	Backend examples that show how bluetape4k modules fit together in application code.
`exposed-workshop`	JetBrains Exposed ORM examples covering schema modeling, transactions, testing, and multi-database verification.
`exposed-r2dbc-workshop`	Exposed R2DBC examples for coroutine-friendly relational persistence.
`timefold-workshop`	Timefold Solver examples for constraint-solving and scheduling problems.

clinic-appointment is a concrete application built as a private-clinic appointment management system.

It demonstrates how the ecosystem can be applied beyond library code:

appointment state transitions from request to completion, including cancellation and reassignment
Timefold Solver scheduling for doctors, rooms, equipment, business hours, and hard/soft constraints
Spring Boot 4 REST APIs with JWT authentication, Flyway migrations, and Swagger UI
Redis-backed leader election for high-availability notification delivery
Resilience4j circuit breaker, retry, and bulkhead patterns for operational reliability
Angular frontend for appointment search, creation, and status changes
modular backend structure across domain, events, solver, notification, API, and frontend layers

It is the kind of app where the blue tape stops being a joke and starts being a reliability strategy.

Want core utilities and Spring infrastructure? Start with bluetape4k-projects.
Working with Exposed? Start with bluetape4k-exposed, then compare examples in exposed-workshop.
Need a real application reference? Read clinic-appointment.
Exploring graph, image, text, AWS, audit, or leader election modules? Pick the matching repository above.

Made for Kotlin backend engineers who know that architecture is cleaner when the tape is blue, documented, tested, and applied only where it belongs.