---
title: Configuration
description: Functional options, the Config struct, and how to customize Relay behavior.
---

Relay uses functional options for wiring dependencies and a `Config` struct for tuning runtime behavior.

## Functional options

The `Relay` struct is configured with functional options passed to `relay.New()`:

```go
r, err := relay.New(
    relay.WithStore(postgresStore),
    relay.WithLogger(slog.Default()),
    relay.WithConcurrency(20),
    relay.WithPollInterval(2 * time.Second),
    relay.WithBatchSize(100),
    relay.WithRequestTimeout(15 * time.Second),
    relay.WithMaxRetries(8),
    relay.WithRetrySchedule(customSchedule),
    relay.WithShutdownTimeout(60 * time.Second),
    relay.WithCacheTTL(time.Minute),
)
```

### Available options

| Option | Purpose | Default |
|--------|---------|---------|
| `WithStore(s)` | Set the persistence backend (required) | -- |
| `WithLogger(l)` | Set the structured logger | `slog.Default()` |
| `WithConcurrency(n)` | Number of delivery worker goroutines | `10` |
| `WithPollInterval(d)` | How often the engine checks for pending deliveries | `1s` |
| `WithBatchSize(n)` | Max deliveries dequeued per poll cycle | `50` |
| `WithRequestTimeout(d)` | HTTP timeout per delivery attempt | `30s` |
| `WithMaxRetries(n)` | Maximum delivery attempts before DLQ | `5` |
| `WithRetrySchedule(s)` | Backoff intervals between retries | `[5s, 30s, 2m, 15m, 2h]` |
| `WithShutdownTimeout(d)` | Max wait for in-flight deliveries on shutdown | `30s` |
| `WithCacheTTL(d)` | TTL for the catalog's in-memory cache (0 = no cache) | `30s` |

## Config struct

```go
type Config struct {
    Concurrency     int
    PollInterval    time.Duration
    BatchSize       int
    RequestTimeout  time.Duration
    MaxRetries      int
    RetrySchedule   []time.Duration
    ShutdownTimeout time.Duration
    CacheTTL        time.Duration
}
```

## Default retry schedule

```go
var DefaultRetrySchedule = []time.Duration{
    5 * time.Second,
    30 * time.Second,
    2 * time.Minute,
    15 * time.Minute,
    2 * time.Hour,
}
```

After all retries are exhausted, the delivery moves to the DLQ.

## Required options

The only required option is `WithStore()`. Without a store, `relay.New()` returns `ErrNoStore`.