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Each iii worker that needs persistence or distribution uses an adapter — a pluggable backend that implements a fixed interface. Swap adapters in iii-config.yaml without touching application code.

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Pattern

workers:
  - name: iii-queue
    config:
      adapter:
        name: redis
        config:
          redis_url: ${REDIS_URL:redis://localhost:6379}
Every adapter entry has two fields:
  • name — the adapter short name
  • config — adapter-specific config (omit if not needed)

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Adapter Reference

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Queue

AdapterNameExternal dependency
Built-inbuiltinNone
RedisredisRedis
RabbitMQrabbitmqRabbitMQ

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builtin

Default. In-process only with retries and DLQ — does not share messages across engine instances. 
adapter:
  name: builtin

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redis

adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

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rabbitmq

adapter:
  name: rabbitmq
  config:
    amqp_url: ${RABBITMQ_URL:amqp://localhost:5672}
    max_attempts: 3
    prefetch_count: 10
    queue_mode: standard   # standard | fifo
For retry behavior, dead-letter queues, and full config reference, see the Queue worker.

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State

AdapterNameExternal dependency
KV StorekvNone
RedisredisRedis
BridgebridgeRemote iii Engine

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kv

Default. Supports in-memory or file-based persistence. 
adapter:
  name: kv
  config:
    store_method: file_based   # in_memory | file_based
    file_path: ./data/state
    save_interval_ms: 5000

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redis

adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

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bridge

Forwards state operations to a remote iii Engine. 
adapter:
  name: bridge

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Stream

AdapterNameExternal dependency
KV StorekvNone
RedisredisRedis

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kv

Default. In-process only. 
adapter:
  name: kv
  config:
    store_method: file_based   # in_memory | file_based
    file_path: ./data/stream_store
    save_interval_ms: 5000

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redis

adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

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Cron

AdapterNameExternal dependency
KV CronkvNone
Redis CronredisRedis

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kv

Default. Process-local locks — jobs may run on every instance in multi-instance deployments. 
adapter:
  name: kv

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redis

Distributed locking via Redis — ensures each job runs only once across all instances. 
adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

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PubSub

AdapterNameExternal dependency
LocallocalNone
RedisredisRedis

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local

Default. In-process broadcast — subscribers must be in the same engine process. 
adapter:
  name: local

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redis

adapter:
  name: redis
  config:
    redis_url: ${REDIS_URL:redis://localhost:6379}

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Choosing an Adapter

Single instanceMulti-instance
QueueBuiltinQueueAdapterRedisAdapter or RabbitMQAdapter
StateKvStore (file_based)RedisAdapter
StreamKvStoreRedisAdapter
CronKvCronAdapterRedisCronAdapter
PubSubLocalAdapterRedisAdapter
Use ${VAR:default} syntax in iii-config.yaml to switch adapters per environment without changing the file:
redis_url: ${REDIS_URL:redis://localhost:6379}