Compatibility

What is tested, what is supported but not tested, and what is not supported. "Tested" means a CI job or an integration test in the repository runs against it; the Stability policy says how this list changes.

Runtimes

	Status	Evidence
Node.js 22 (22.12 and newer)	tested	CI test matrix 22.x and 24.x
Node.js 24	tested	CI test matrix
CommonJS and ESM	built and type-checked for both	every package ships import and require entry points with their own types; publint and attw check them in CI
NestJS 11 and 12	tested	CI job nestjs compat re-resolves @nestjs/* to each major and runs the typecheck and the @relaybus/nestjs tests
Bun, Deno	untested, not supported

Stores

Store	Versions	Notes
PostgreSQL	13 and newer; integration tests run on 13 and 17	pg is the primary client and the only one with prepared statements.
pg pool or client	tested	PostgresEventStore({ pool })
Kysely	integration tested	createKyselyExecutor
Knex	integration tested
TypeORM	integration tested
Drizzle	integration tested
Prisma	integration tested (Client 5.22, 6.19 and 7.10, @prisma/adapter-pg)	Full contract suite on a generated client. Give the store your pg pool as well for prepared statements and wake-ups at commit.
MongoDB	6.0 and newer, integration tests on 7	Replica set or sharded cluster only: relaybus uses multi-document transactions. A single-node replica set is enough for development. Driver mongodb 6 or 7; Mongoose sessions work.

Transports

Transport	Tested	Notes
Kafka with kafkajs 2.2.x	integration tested against a real broker (confluentinc/cp-kafka:7.5.0), 2.2.4	kafkajs is unmaintained. It stays supported and is the default client; prefer Confluent for new services.
Kafka with @confluentinc/kafka-javascript	integration tested against the same broker, 1.11.0 (KafkaJS-compatible API)	Recommended: maintained and librdkafka based. Pass client: 'confluent'; the transport puts its settings in the kafkaJS blocks and follows the group through rebalance_cb. Peer range ^1.11.0. See Choosing a client.
RabbitMQ	integration tested on RabbitMQ 4 (rabbitmq:4-alpine); 3.13 or newer is required	Quorum queues are used for the queue and the dead-letter queue. amqplib 0.10 or newer.

Codecs

Codec	Kafka	RabbitMQ
cloudEventsBinary (default)	tested, golden bytes	tested, golden bytes
cloudEventsStructured	tested	tested
jsonEnvelope({ ... })	tested	tested
{ encode, decode } (custom)	tested	tested

Explicitly unsupported

These are not planned for the current release line; no store or transport exists for them.

	Why / what to use
MySQL, SQL Server, SQLite	No store. relaybus needs SELECT ... FOR UPDATE SKIP LOCKED-style claims, advisory locks and a transactional outbox in your database; PostgreSQL and MongoDB are the stores.
MongoDB standalone	No multi-document transactions. Use a replica set.
Amazon SQS and SNS, NATS, Google Pub/Sub, Redis Streams	No transport. Implement the small Transport interface (publish, subscribe, close) yourself if you need one; it is not tested by relaybus.
Bun, Deno	Untested.

Serverless and short-lived processes

relaybus delivers from a long-running dispatcher: it claims deliveries on a poll and, on PostgreSQL, wakes on LISTEN/NOTIFY, and it holds leases while a handler runs. A process that is frozen or killed between requests cannot do that.

• Publishing from a function works: publish inside your database transaction and let the commit make the event durable. Set dispatcher: { enabled: false } in the function and run the dispatcher in a long-running worker (Tuning).
• Dispatching from a function is possible only by calling bus.runOnce() per invocation (one batch) and finishing before the platform freezes the process. Expect higher latency, no NOTIFY wake-ups, and leases that expire when an invocation is cut short, which makes the delivery run again (at-least-once holds).
• Behind a connection pooler in transaction mode, use the settings in Tuning (wakeUp: 'poll', preparedStatements: false where needed).

Where this is checked

CI (.github/workflows/ci.yml): quality (Prettier, ESLint, typecheck, performance budgets), test on Node 22 and 24 with 100 % coverage thresholds, build (all packages, publint, attw), nestjs-compat on NestJS 11 and 12. Integration tests start their databases and brokers with Testcontainers.