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arkd is configured via environment variables. This page documents settings that affect runtime behavior, gRPC transport, and API performance.
All variables are passed as environment variables.

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gRPC Transport

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MAX_CONCURRENT_STREAMS

Controls the maximum number of concurrent HTTP/2 streams allowed per gRPC connection. When to tune this:
  • High-traffic operators serving many simultaneous clients should increase this value.
  • Setting it to 0 is invalid and will prevent arkd from starting (validation error at boot).
As of arkd PR #978, both the secure and insecure gRPC listeners respect this setting. Prior to this change, the HTTP/2 server used the Go default.

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Split Unary vs. Streaming Connections

arkd internally routes unary RPCs and server-side streaming RPCs through separate gRPC transports. This is an implementation detail — no configuration is required — but it has observable effects:
  • Health checks use the unary transport. They remain responsive even when streaming connections experience backpressure or reconnects.
  • GetEventStream / GetTransactionsStream use the streaming transport with jittered reconnect backoff.
  • The admin service (wallet operations, config updates) runs on a dedicated gateway separate from the public client endpoints.
This separation improves reliability under load and makes liveness reporting more accurate. See arkd PR #979.

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GetInfo Caching

GetInfo responses are now cached in memory at startup to reduce database load on high-frequency calls.

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Cache behavior

What is cached:
  • Dust amounts and min/max UTXO/VTXO amounts
  • Scheduled session configuration (round intervals, expiry delays)
  • Fee formula parameters
  • Server signer public key and network type
  • Market hours configuration
What is NOT cached:
  • Real-time VTXO states and balances (always queried live)
  • Transaction history
If you update server configuration outside of the standard admin RPCs (e.g., by directly modifying the database), call RefreshInfoCache via the admin API to ensure GetInfo returns up-to-date values.
See arkd PR #976.

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Other Notable Environment Variables

For reference, the full list of environment variables is defined in internal/config/config.go. Key variables include:
All environment variables require the ARKD_ prefix.