---
title: Custom Store
description: Implement your own store backend.
---

Relay's store layer is interface-based. You can implement a custom backend by satisfying the `store.Store` interface.

## The interface

```go
type Store interface {
    catalog.Store
    endpoint.Store
    event.Store
    delivery.Store
    dlq.Store

    Migrate(ctx context.Context) error
    Ping(ctx context.Context) error
    Close() error
}
```

This composes five subsystem interfaces plus three lifecycle methods.

## Subsystem interfaces

### catalog.Store

```go
type Store interface {
    RegisterType(ctx context.Context, et *EventType) error
    GetType(ctx context.Context, name string) (*EventType, error)
    GetTypeByID(ctx context.Context, etID id.ID) (*EventType, error)
    ListTypes(ctx context.Context, opts ListOpts) ([]*EventType, error)
    MatchTypes(ctx context.Context, eventType string) ([]*EventType, error)
    DeleteType(ctx context.Context, name string) error
}
```

### endpoint.Store

```go
type Store interface {
    CreateEndpoint(ctx context.Context, ep *Endpoint) error
    GetEndpoint(ctx context.Context, epID id.ID) (*Endpoint, error)
    UpdateEndpoint(ctx context.Context, ep *Endpoint) error
    DeleteEndpoint(ctx context.Context, epID id.ID) error
    ListEndpoints(ctx context.Context, tenantID string, opts ListOpts) ([]*Endpoint, error)
    SetEnabled(ctx context.Context, epID id.ID, enabled bool) error
    Resolve(ctx context.Context, tenantID string, eventType string) ([]*Endpoint, error)
}
```

### delivery.Store

```go
type Store interface {
    EnqueueBatch(ctx context.Context, deliveries []*Delivery) error
    Dequeue(ctx context.Context, limit int) ([]*Delivery, error)
    GetDelivery(ctx context.Context, delID id.ID) (*Delivery, error)
    UpdateDelivery(ctx context.Context, d *Delivery) error
    ListByEndpoint(ctx context.Context, epID id.ID, opts ListOpts) ([]*Delivery, error)
    ListByEvent(ctx context.Context, evtID id.ID, opts ListOpts) ([]*Delivery, error)
}
```

## Implementation tips

1. Start with the memory store source as a reference (`store/memory/store.go`).
2. The `Resolve()` method must filter by tenant ID, enabled status, and match event type patterns against endpoint subscriptions.
3. `Dequeue()` should atomically claim pending deliveries whose `NextAttemptAt` is in the past.
4. `Migrate()` should be idempotent (safe to call multiple times).
5. Run the existing test suite against your implementation to verify correctness.