# Kotlin Coroutines > Coroutine usage guardrails for Kotlin backend reviewers Use when this capability is needed. - Skill: `tomevault-io/kotlin-coroutines` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/kotlin-coroutines` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/kotlin-coroutines/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/kotlin-coroutines --- ## Mission - Preserve non-blocking performance characteristics by enforcing clear coroutine boundaries. - Prevent thread pool exhaustion, deadlocks, and latency spikes caused by mixing blocking and suspend flows. ## Red Flags - Mixing blocking and suspending calls inside the same function without isolating the blocking work. - Calling `runBlocking` anywhere other than top-level entrypoints (resources, `main`) or when explicitly bridging to blocking code with the correct dispatcher. - Using `async { ... }.await()` immediately, or using `async` just to change dispatchers. - Wiring `AsyncResponse` (Dropwizard) to wrap blocking DAO calls instead of true suspend flows. ## Review Checklist - Verify suspending chains remain suspend: bubble `suspend` up through managers/resources or wrap legacy blocking code with `withContext(Dispatchers.IO)`. - Ensure blocking functions stay blocking all the way up the call stack; prefer dedicated blocking helpers (e.g., `getUserBlocking`) rather than ad-hoc `runBlocking`. - When bridging to suspend from non-suspend contexts, check the dispatcher passed to `runBlocking` matches the underlying workload (usually `Dispatchers.IO`). - Confirm `AsyncResponse` is only applied to non-blocking suspend flows (Cosmos, service clients with `await`/`executeAwait`). Flag usages that simply wrap JDBI or other blocking calls. - Look for nested coroutine builders. Replace `async/await` pairs used sequentially with direct calls; use concurrent `async` only when awaiting later. - Ensure dispatcher changes use `withContext`, not `async`, and that blocking calls inside suspend functions are guarded with the appropriate context. ## Tooling Tips - `Grep` for `runBlocking`, `.await()`, `executeSync`, or `AsyncResponse` to inspect how coroutines and blocking APIs mix. - `Read` affected managers/resources to trace whether suspend functions bubble correctly. - `Glob` modules like `*Manager.kt`, `*Resource.kt`, and `*Dao.kt` when you need broader context about call chains. --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/sids) — claim your Tome and manage your conversions.