Delivery Modes
The delivery.mode field on an edge controls the transport layer and durability guarantee.
direct
In-process function call. No broker, no serialization. Fastest path.
- Transport: in-process
- Durability: none
- Best for: fast local transforms within the same process
Protocol resolution
When both nodes share the same language runtime (e.g. Go → Go), direct is a
true in-process call. When the source and target run in different languages
(e.g. Go → Python), the runtime transparently upgrades the call to gRPC while
keeping the direct delivery semantics (no broker, no durability).
| Source lang | Target lang | Actual transport |
|---|---|---|
| Same | Same | In-process function call |
| Different | Different | gRPC (transparent upgrade) |
See Communication Protocols for all supported protocols.
ephemeral
Redis / NATS / RabbitMQ queue. Survives brief spikes but not process restarts.
- Transport: Redis / NATS / RabbitMQ
- Durability: low
- Best for: burst smoothing, rate-limiting
checkpoint
Mongo / Redis / Postgres backed. Progress is saved at each stage, enabling replay from any point.
- Transport: Mongo / Redis / Postgres
- Durability: stage-level
- Best for: high-throughput pipelines that need replay
durable
Mongo / Postgres backed, packet-level acknowledgement. Every message is persisted before processing begins.
- Transport: Mongo / Postgres
- Durability: packet-level
- Best for: business-critical steps (payments, order fulfilment)
stream
Kafka / Redis / NATS durable stream. Supports fan-out to multiple consumers and external integration.
- Transport: Kafka / Redis / NATS
- Durability: durable stream
- Best for: external integration, fan-out, audit logging
Choosing a mode
| Scenario | Recommended mode |
|---|---|
| In-process transform | direct |
| Queue spikes, low stakes | ephemeral |
| Long pipeline, need replay | checkpoint |
| Money, orders, legal | durable |
| External consumers, fan-out | stream |
Delivery mode vs communication protocol
Delivery mode and communication protocol are two separate concerns:
- Delivery mode (on an edge) defines how packets flow between nodes — the durability guarantees and buffering strategy.
- Communication protocol (on an edge) defines the wire protocol for a specific connection — gRPC, NATS, Redis, etc. Nodes declare which protocols they support via
runtime.supports.
They compose independently. An edge using NATS as its protocol can still have durable delivery mode — the runtime handles the translation between the edge's delivery transport and the connection's wire protocol.
See Communication Protocols for all 9 supported protocols.