Configuration

The configuration system mirrors modern ASP.NET Core conventions. Bind strongly typed options, validate them on startup, and the runtime refuses to boot if something important is missing.

Register options with validation

Program.cs

using Asynkron.DurableFunctions.Extensions;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddDurableFunctions(builder.Configuration); // registers runtime + validates options

Configuration lives under the DurableFunctions section. The defaults are production-friendly, but you can override the properties that matter.

appsettings.json

{
  "DurableFunctions": {
    "Storage": {
      "Provider": "PostgreSQL",
      "PostgreSQL": {
        "ConnectionString": "Host=localhost;Database=durablefunctions;Username=user;Password=pass;SSL Mode=Require;",
        "RequireSsl": true,
        "ValidateConnectivity": true
      }
    },
    "Runtime": {
      "HostId": "worker-01",
      "LeaseTimeout": "00:00:30",
      "LeaseRenewalInterval": "00:00:10",
      "PollingInterval": "00:00:00.100",
      "MaxConcurrentOrchestrations": 100
    },
    "Security": {
      "MaxInputSize": 65536,
      "MaxSerializationDepth": 32,
      "ValidateInputs": true
    }
  }
}

Validation catches typos (for example, missing HostId or invalid connection strings) during startup rather than at 3 a.m. in production.

Runtime options

Option	Why it matters
HostId	Identifies the worker in logs and lease records. Must be unique across all hosts.
LeaseTimeout & LeaseRenewalInterval	Control multi-host safety. Shorter leases recover faster after crashes; longer leases reduce database churn.
PollingInterval	Lower values reduce latency but increase database load. The default 100ms is a good starting point.
MaxConcurrentOrchestrations	Limit to protect downstream systems. When set, the runtime pauses polling when the limit is reached.

Storage providers

Provider	When to use	Key settings
SQLite	Local development, embedded appliances, or lightweight single-node deployments.	ConnectionString must include Data Source. Combine with Cache=Shared and Journal Mode=WAL when multiple workers share a file.
PostgreSQL	Production-grade clusters that need high availability and observability.	Provide a full connection string. Enable SSL (RequireSsl) and optionally set ValidateConnectivity to true to fail fast when credentials are wrong.
InMemory	Tests and throwaway prototypes.	No extra configuration. Data is lost on restart.

Both relational providers migrate the schema automatically. With concurrency stores the following columns appear in the DurableFunctionStates table: Version, LeaseOwner, LeaseExpiresAt. Indexes back these columns so lease lookups stay fast.

Security limits

Durable workflows often accept large payloads. Apply limits to keep requests reasonable and guard against runaway recursion.

• MaxInputSize – rejects payloads larger than the configured number of bytes.
• MaxSerializationDepth – prevents deserialising deeply nested JSON structures.
• ValidateInputs – enable to perform schema validation and reject invalid payloads before execution.

Combine these with web-host level limits (for example, Kestrel request size limits) for layered defence.