A source-verified, production-first guide to Cash App's open-source Kotlin microservice container.
Misk is the open-source Kotlin microservice container that runs hundreds of services at Cash App. Here's what a container is, how it differs from Spring Boot and Ktor, and when to reach for it.
A hands-on misk getting started walkthrough: the Gradle and BOM setup, the MiskApplication entry point, the module list, config YAML, and running the exemplar service locally.
How misk dependency injection works: KAbstractModule, bindings, qualifiers, and multibindings in Kotlin — and why Misk chose Guice over Spring-style component scanning.
How the misk service lifecycle works: Guava ServiceManager, dependency ordering with dependsOn and enhancedBy, the ReadyService pattern, warmup, and misk graceful shutdown that drains in-flight work.
Write a misk web action: WebAction, @Get/@Post, path and query params, typed request and response bodies, and status control with Response<T> — plus why Misk favors one action class per endpoint.
How Misk moves bytes: JSON marshalling with Moshi, form-encoded bodies, misk multipart upload handling via MultipartReader, and file downloads with Content-Disposition.
A guide to the misk interceptor model: NetworkInterceptor vs ApplicationInterceptor, where each sits in the request pipeline, the Factory that opts them in per action, and how to write your own.
Build a misk grpc endpoint with protobuf and Wire: define the proto, generate server interfaces, implement a gRPC action, and get an automatic JSON variant of every protobuf action.
How misk authentication and access control work: @Authenticated, the MiskCaller model of services and capabilities, custom access annotations, the AccessInterceptor that enforces them, and audit logging.
Externalize complex authorization with misk opa integration: wire Misk to Open Policy Agent via misk-policy, write type-safe OpaPolicyEngine queries, and test policy locally.
How misk crypto wires Tink primitives from KMS-encrypted keys, and how misk secrets keep credentials out of code, logs, and dashboards via Secret<T> and @Redact.
How misk jdbc wires a real database: misk datasource config, Hikari connection pooling, read/write splitting via reader/writer clusters, and the JDBC-layer Transacter.
How misk hibernate models entities and queries, and how the misk transacter gives you block-based transactions, retries, and replica reads without ever handing you a raw Hibernate session.
How misk schema migration works — versioned .sql files, the schema_version table, the standalone Gradle plugin, and why it's a credible misk flyway alternative.
Why misk sqldelight and jOOQ are the type-safe alternatives to Hibernate, plus misk vitess sharding for horizontal MySQL scale and the Vitess Gradle plugin.
How misk redis and misk caching work: the Jedis-backed Redis client, the newer Lettuce module, RedisModule wiring, RedisConfig YAML, and a FakeRedis for tests.
How misk rate limiting and misk tokens work: the wisp RateLimiter backed by Bucket4j (Redis, MySQL, DynamoDB), and TokenGenerator for unguessable IDs.
How the misk job queue works: defining handlers, enqueuing, and the misk sqs (misk-aws2-sqs) backend — plus the transactional spooling table and its exactly-once-ish guarantee.
How misk cron schedules recurring work: the @CronPattern annotation, the Runnable contract, CronModule wiring, and the lease-based coordination that stops every replica from firing the same job.
How a misk distributed lease works and how to use it for misk leader election: the Lease/LeaseManager API, the SQL and cluster-aware backends, and the time-bound correctness caveats.
A deeper look at misk config and misk environments: the Deployment model, the full YAML resolution and merge order, Secret<T> loading, redaction, and Wisp's standalone config and deployment helpers.
How misk observability fits together: misk metrics prometheus counters, gauges and histograms, structured logging with MDC tags, sampling, and OpenTracing-backed tracing on Datadog.
How misk testing works: @MiskTest stands up a real injector, fakes ship as modules, and WebTestClient gives you fast integration tests against a running server — plus action registration checks.
How the misk admin dashboard works and how to build tabs on its misk hotwire tailwind stack — kotlinx.html server-side rendering, the deprecated React misk-web, and AdminDashboardAccess gating.
Turn a Misk service into a Model Context Protocol server with misk mcp: define tools, resources, and prompts, then expose them to LLMs over StreamableHTTP or WebSocket.