refactor: self-contained delivery tasks — engine delivers without DB reads in happy path

The webhook handler now builds DeliveryTask structs carrying all target
config and event data inline (for bodies ≤16KB) and sends them through
the delivery channel. In the happy path, the engine delivers without
reading from any database — it only writes to record delivery results.

For large bodies (≥16KB), Body is nil and the engine fetches it from the
per-webhook database on demand. Retry timers also carry the full
DeliveryTask, so retries avoid unnecessary DB reads.

The database is used for crash recovery only: on startup the engine scans
for interrupted pending/retrying deliveries and re-queues them.

Implements owner feedback from issue #15:
> the message in the <=16KB case should have everything it needs to do
> its delivery. it shouldn't touch the db until it has a success or
> failure to record.

internal/delivery/engine.go

@@ -27,7 +27,7 @@ const (
 	retryChannelSize = 1000
 
 	// MaxInlineBodySize is the maximum event body size that will be carried
-	// inline in a Notification through the channel. Bodies at or above this
+	// inline in a DeliveryTask through the channel. Bodies at or above this
 	// size are left nil and fetched from the per-webhook database on demand.
 	// This keeps channel buffer memory bounded under high traffic.
 	MaxInlineBodySize = 16 * 1024
@@ -39,31 +39,42 @@ const (
 	maxBodyLog = 4096
 )
 
-// Notification carries event data through the delivery notification channel.
-// The Body field is a pointer: non-nil for payloads under MaxInlineBodySize
-// (16 KB), nil for larger payloads. When nil, the engine fetches the body
-// from the per-webhook database using EventID. This keeps channel buffer
-// memory bounded regardless of payload sizes during high traffic.
-type Notification struct {
-	WebhookID   string
-	EventID     string
+// DeliveryTask contains everything needed to deliver an event to a single
+// target. In the ≤16KB happy path, Body is non-nil and the engine delivers
+// without touching any database — it trusts that the webhook handler wrote
+// the records correctly. Only after a delivery attempt (success or failure)
+// does the engine write to the DB to record the result.
+//
+// When Body is nil (payload ≥ MaxInlineBodySize), the engine fetches the
+// body from the per-webhook database using EventID before delivering.
+type DeliveryTask struct {
+	DeliveryID string // ID of the Delivery record (for recording results)
+	EventID    string // Event ID (for DB lookup if body is nil)
+	WebhookID  string // Webhook ID (for per-webhook DB access)
+
+	// Target info (from main DB, included at notification time)
+	TargetID     string
+	TargetName   string
+	TargetType   database.TargetType
+	TargetConfig string // JSON config (URL, headers, etc.)
+	MaxRetries   int
+
+	// Event data (inline for ≤16KB bodies)
 	Method      string
-	Headers     string
+	Headers     string // JSON
 	ContentType string
-	Body        *string // nil if body >= MaxInlineBodySize; fetch from DB by EventID
+	Body        *string // nil if body ≥ MaxInlineBodySize; fetch from DB by EventID
+
+	// AttemptNum tracks the delivery attempt number. Set to 1 for the
+	// initial delivery and incremented for each retry. This avoids a DB
+	// query to count prior results in the hot path.
+	AttemptNum int
 }
 
 // Notifier is the interface for notifying the delivery engine about new
 // deliveries. Implemented by Engine and injected into handlers.
 type Notifier interface {
-	Notify(n Notification)
-}
-
-// retryRequest carries the information needed to retry a specific delivery.
-// Sent from timer goroutines to the engine's retry channel.
-type retryRequest struct {
-	webhookID  string
-	deliveryID string
+	Notify(tasks []DeliveryTask)
 }
 
 // HTTPTargetConfig holds configuration for http and retry target types.
@@ -84,13 +95,15 @@ type EngineParams struct {
 }
 
 // Engine processes queued deliveries in the background using an
-// event-driven architecture. New deliveries are signaled via a buffered
-// channel from the webhook handler and processed immediately. Failed
-// deliveries that need retry are scheduled via Go timers with exponential
-// backoff — each timer fires into a separate retry channel when the
-// backoff period expires. The database stores delivery status for crash
-// recovery only; on startup the engine scans for interrupted deliveries
-// and re-queues them.
+// event-driven architecture. New deliveries arrive as self-contained
+// DeliveryTask slices via a buffered channel from the webhook handler.
+// In the happy path (body ≤ 16KB), the engine delivers without reading
+// from any database — it only writes to record results. Failed deliveries
+// that need retry are scheduled via Go timers with exponential backoff;
+// each timer fires into a separate retry channel carrying the full
+// DeliveryTask so retries also avoid unnecessary DB reads. The database
+// stores delivery status for crash recovery only; on startup the engine
+// scans for interrupted deliveries and re-queues them.
 type Engine struct {
 	database  *database.Database
 	dbManager *database.WebhookDBManager
@@ -98,8 +111,8 @@ type Engine struct {
 	client    *http.Client
 	cancel    context.CancelFunc
 	wg        sync.WaitGroup
-	notifyCh  chan Notification
-	retryCh   chan retryRequest
+	notifyCh  chan []DeliveryTask
+	retryCh   chan DeliveryTask
 }
 
 // New creates and registers the delivery engine with the fx lifecycle.
@@ -111,8 +124,8 @@ func New(lc fx.Lifecycle, params EngineParams) *Engine {
 		client: &http.Client{
 			Timeout: httpClientTimeout,
 		},
-		notifyCh: make(chan Notification, notifyChannelSize),
-		retryCh:  make(chan retryRequest, retryChannelSize),
+		notifyCh: make(chan []DeliveryTask, notifyChannelSize),
+		retryCh:  make(chan DeliveryTask, retryChannelSize),
 	}
 
 	lc.Append(fx.Hook{
@@ -144,19 +157,17 @@ func (e *Engine) stop() {
 	e.log.Info("delivery engine stopped")
 }
 
-// Notify signals the delivery engine that new deliveries are available.
-// This is called by the webhook handler after creating delivery records.
-// The notification carries the event data inline (with body pointer
-// semantics for memory efficiency). The call is non-blocking; if the
-// channel is full, a warning is logged and the deliveries will be
-// recovered on the next engine restart.
-func (e *Engine) Notify(n Notification) {
+// Notify signals the delivery engine that new deliveries are ready.
+// Called by the webhook handler after creating delivery records. Each
+// DeliveryTask carries all data needed for delivery in the ≤16KB case.
+// The call is non-blocking; if the channel is full, a warning is logged
+// and the deliveries will be recovered on the next engine restart.
+func (e *Engine) Notify(tasks []DeliveryTask) {
 	select {
-	case e.notifyCh <- n:
+	case e.notifyCh <- tasks:
 	default:
 		e.log.Warn("delivery notification channel full, deliveries will be recovered on restart",
-			"webhook_id", n.WebhookID,
-			"event_id", n.EventID,
+			"task_count", len(tasks),
 		)
 	}
 }
@@ -174,10 +185,10 @@ func (e *Engine) run(ctx context.Context) {
 		select {
 		case <-ctx.Done():
 			return
-		case n := <-e.notifyCh:
-			e.processNotification(ctx, n)
-		case req := <-e.retryCh:
-			e.processRetryDelivery(ctx, req)
+		case tasks := <-e.notifyCh:
+			e.processDeliveryTasks(ctx, tasks)
+		case task := <-e.retryCh:
+			e.processRetryTask(ctx, task)
 		}
 	}
 }
@@ -209,9 +220,9 @@ func (e *Engine) recoverInFlight(ctx context.Context) {
 }
 
 // recoverWebhookDeliveries recovers pending and retrying deliveries for
-// a single webhook. Pending deliveries are processed directly (loading
-// event data from DB); retrying deliveries get timers scheduled based on
-// the elapsed time since the last attempt.
+// a single webhook. This is the recovery path — it reads everything from
+// the database since there are no in-memory notifications available after
+// a restart.
 func (e *Engine) recoverWebhookDeliveries(ctx context.Context, webhookID string) {
 	webhookDB, err := e.dbManager.GetDB(webhookID)
 	if err != nil {
@@ -256,6 +267,28 @@ func (e *Engine) recoverWebhookDeliveries(ctx context.Context, webhookID string)
 			Count(&resultCount)
 		attemptNum := int(resultCount)
 
+		// Load event for this delivery
+		var event database.Event
+		if err := webhookDB.First(&event, "id = ?", d.EventID).Error; err != nil {
+			e.log.Error("failed to load event for retrying delivery recovery",
+				"delivery_id", d.ID,
+				"event_id", d.EventID,
+				"error", err,
+			)
+			continue
+		}
+
+		// Load target from main DB
+		var target database.Target
+		if err := e.database.DB().First(&target, "id = ?", d.TargetID).Error; err != nil {
+			e.log.Error("failed to load target for retrying delivery recovery",
+				"delivery_id", d.ID,
+				"target_id", d.TargetID,
+				"error", err,
+			)
+			continue
+		}
+
 		// Calculate remaining backoff from last attempt
 		remaining := time.Duration(0)
 
@@ -278,6 +311,30 @@ func (e *Engine) recoverWebhookDeliveries(ctx context.Context, webhookID string)
 			}
 		}
 
+		// Build task from DB data. Use body pointer semantics: inline
+		// for small bodies, nil for large ones (will be fetched on retry).
+		var bodyPtr *string
+		if len(event.Body) < MaxInlineBodySize {
+			bodyStr := event.Body
+			bodyPtr = &bodyStr
+		}
+
+		task := DeliveryTask{
+			DeliveryID:   d.ID,
+			EventID:      d.EventID,
+			WebhookID:    webhookID,
+			TargetID:     target.ID,
+			TargetName:   target.Name,
+			TargetType:   target.Type,
+			TargetConfig: target.Config,
+			MaxRetries:   target.MaxRetries,
+			Method:       event.Method,
+			Headers:      event.Headers,
+			ContentType:  event.ContentType,
+			Body:         bodyPtr,
+			AttemptNum:   attemptNum + 1,
+		}
+
 		e.log.Info("recovering retrying delivery",
 			"webhook_id", webhookID,
 			"delivery_id", d.ID,
@@ -285,42 +342,149 @@ func (e *Engine) recoverWebhookDeliveries(ctx context.Context, webhookID string)
 			"remaining_backoff", remaining,
 		)
 
-		e.scheduleRetry(webhookID, d.ID, remaining)
+		e.scheduleRetry(task, remaining)
 	}
 }
 
-// processNotification handles a delivery notification from the webhook
-// handler. It uses the inline event data from the notification (avoiding
-// a DB round-trip for the event) and only fetches the body from DB when
-// it was too large to carry inline (Body pointer is nil).
-func (e *Engine) processNotification(ctx context.Context, n Notification) {
-	webhookDB, err := e.dbManager.GetDB(n.WebhookID)
+// processDeliveryTasks handles a batch of delivery tasks from the webhook
+// handler. In the happy path (body ≤ 16KB), the engine delivers without
+// reading from any database — it trusts the handler's inline data and
+// only touches the DB to record results. For large bodies (body > 16KB),
+// the body is fetched from the per-webhook database on demand.
+func (e *Engine) processDeliveryTasks(ctx context.Context, tasks []DeliveryTask) {
+	if len(tasks) == 0 {
+		return
+	}
+
+	// All tasks in a batch share the same webhook ID
+	webhookID := tasks[0].WebhookID
+	webhookDB, err := e.dbManager.GetDB(webhookID)
 	if err != nil {
 		e.log.Error("failed to get webhook database",
-			"webhook_id", n.WebhookID,
+			"webhook_id", webhookID,
 			"error", err,
 		)
 		return
 	}
 
-	// Build the Event from the notification's inline data
-	event := database.Event{
-		Method:      n.Method,
-		Headers:     n.Headers,
-		ContentType: n.ContentType,
-	}
-	event.ID = n.EventID
-	event.WebhookID = n.WebhookID
+	// For the large-body case, we may need to fetch the event body once
+	// for all tasks sharing the same event. Cache it here.
+	var fetchedBody *string
 
-	if n.Body != nil {
-		event.Body = *n.Body
+	for i := range tasks {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+
+		task := &tasks[i]
+
+		// Build Event from task data
+		event := database.Event{
+			Method:      task.Method,
+			Headers:     task.Headers,
+			ContentType: task.ContentType,
+		}
+		event.ID = task.EventID
+		event.WebhookID = task.WebhookID
+
+		if task.Body != nil {
+			// Happy path: body inline, no DB read needed
+			event.Body = *task.Body
+		} else {
+			// Large body path: fetch from per-webhook DB (once per batch)
+			if fetchedBody == nil {
+				var dbEvent database.Event
+				if err := webhookDB.Select("body").
+					First(&dbEvent, "id = ?", task.EventID).Error; err != nil {
+					e.log.Error("failed to fetch event body from database",
+						"event_id", task.EventID,
+						"error", err,
+					)
+					continue
+				}
+				fetchedBody = &dbEvent.Body
+			}
+			event.Body = *fetchedBody
+		}
+
+		// Build Target from task data (no main DB query needed)
+		target := database.Target{
+			Name:       task.TargetName,
+			Type:       task.TargetType,
+			Config:     task.TargetConfig,
+			MaxRetries: task.MaxRetries,
+		}
+		target.ID = task.TargetID
+
+		// Build Delivery struct for the processing chain
+		d := &database.Delivery{
+			EventID:  task.EventID,
+			TargetID: task.TargetID,
+			Status:   database.DeliveryStatusPending,
+			Event:    event,
+			Target:   target,
+		}
+		d.ID = task.DeliveryID
+
+		e.processDelivery(ctx, webhookDB, d, task)
+	}
+}
+
+// processRetryTask handles a single delivery task fired by a retry timer.
+// The task carries all data needed for delivery (same as the initial
+// notification). The only DB read is a status check to verify the delivery
+// hasn't been cancelled or resolved while the timer was pending.
+func (e *Engine) processRetryTask(ctx context.Context, task DeliveryTask) {
+	webhookDB, err := e.dbManager.GetDB(task.WebhookID)
+	if err != nil {
+		e.log.Error("failed to get webhook database for retry",
+			"webhook_id", task.WebhookID,
+			"delivery_id", task.DeliveryID,
+			"error", err,
+		)
+		return
+	}
+
+	// Verify delivery is still in retrying status (may have been
+	// cancelled or manually resolved while the timer was pending)
+	var d database.Delivery
+	if err := webhookDB.Select("id", "status").
+		First(&d, "id = ?", task.DeliveryID).Error; err != nil {
+		e.log.Error("failed to load delivery for retry",
+			"delivery_id", task.DeliveryID,
+			"error", err,
+		)
+		return
+	}
+
+	if d.Status != database.DeliveryStatusRetrying {
+		e.log.Debug("skipping retry for delivery no longer in retrying status",
+			"delivery_id", d.ID,
+			"status", d.Status,
+		)
+		return
+	}
+
+	// Build Event from task data
+	event := database.Event{
+		Method:      task.Method,
+		Headers:     task.Headers,
+		ContentType: task.ContentType,
+	}
+	event.ID = task.EventID
+	event.WebhookID = task.WebhookID
+
+	if task.Body != nil {
+		event.Body = *task.Body
 	} else {
-		// Body was too large for inline transport — fetch from DB
+		// Large body: fetch from per-webhook DB
 		var dbEvent database.Event
 		if err := webhookDB.Select("body").
-			First(&dbEvent, "id = ?", n.EventID).Error; err != nil {
-			e.log.Error("failed to fetch event body from database",
-				"event_id", n.EventID,
+			First(&dbEvent, "id = ?", task.EventID).Error; err != nil {
+			e.log.Error("failed to fetch event body for retry",
+				"event_id", task.EventID,
 				"error", err,
 			)
 			return
@@ -328,69 +492,27 @@ func (e *Engine) processNotification(ctx context.Context, n Notification) {
 		event.Body = dbEvent.Body
 	}
 
-	// Query pending deliveries for this specific event
-	var deliveries []database.Delivery
-	result := webhookDB.
-		Where("event_id = ? AND status = ?", n.EventID, database.DeliveryStatusPending).
-		Find(&deliveries)
-
-	if result.Error != nil {
-		e.log.Error("failed to query pending deliveries",
-			"webhook_id", n.WebhookID,
-			"event_id", n.EventID,
-			"error", result.Error,
-		)
-		return
+	// Build Target from task data
+	target := database.Target{
+		Name:       task.TargetName,
+		Type:       task.TargetType,
+		Config:     task.TargetConfig,
+		MaxRetries: task.MaxRetries,
 	}
+	target.ID = task.TargetID
 
-	if len(deliveries) == 0 {
-		return
-	}
+	// Populate the delivery with event and target for processing
+	d.EventID = task.EventID
+	d.TargetID = task.TargetID
+	d.Event = event
+	d.Target = target
 
-	// Collect unique target IDs and load targets from the main DB
-	seen := make(map[string]bool)
-	targetIDs := make([]string, 0, len(deliveries))
-	for _, d := range deliveries {
-		if !seen[d.TargetID] {
-			targetIDs = append(targetIDs, d.TargetID)
-			seen[d.TargetID] = true
-		}
-	}
-
-	var targets []database.Target
-	if err := e.database.DB().Where("id IN ?", targetIDs).Find(&targets).Error; err != nil {
-		e.log.Error("failed to load targets from main DB", "error", err)
-		return
-	}
-
-	targetMap := make(map[string]database.Target, len(targets))
-	for _, t := range targets {
-		targetMap[t.ID] = t
-	}
-
-	for i := range deliveries {
-		select {
-		case <-ctx.Done():
-			return
-		default:
-			target, ok := targetMap[deliveries[i].TargetID]
-			if !ok {
-				e.log.Error("target not found for delivery",
-					"delivery_id", deliveries[i].ID,
-					"target_id", deliveries[i].TargetID,
-				)
-				continue
-			}
-			deliveries[i].Event = event
-			deliveries[i].Target = target
-			e.processDelivery(ctx, webhookDB, &deliveries[i])
-		}
-	}
+	e.processDelivery(ctx, webhookDB, &d, &task)
 }
 
 // processWebhookPendingDeliveries queries a single webhook's database for
 // all pending deliveries and processes them. Used for crash recovery where
-// we don't have inline event data — everything is loaded from the DB.
+// we don't have in-memory notifications — everything is loaded from the DB.
 func (e *Engine) processWebhookPendingDeliveries(ctx context.Context, webhookID string) {
 	webhookDB, err := e.dbManager.GetDB(webhookID)
 	if err != nil {
@@ -454,90 +576,59 @@ func (e *Engine) processWebhookPendingDeliveries(ctx context.Context, webhookID
 				continue
 			}
 			deliveries[i].Target = target
-			e.processDelivery(ctx, webhookDB, &deliveries[i])
+
+			// Build task from DB data for the recovery path
+			bodyStr := deliveries[i].Event.Body
+			task := &DeliveryTask{
+				DeliveryID:   deliveries[i].ID,
+				EventID:      deliveries[i].EventID,
+				WebhookID:    webhookID,
+				TargetID:     target.ID,
+				TargetName:   target.Name,
+				TargetType:   target.Type,
+				TargetConfig: target.Config,
+				MaxRetries:   target.MaxRetries,
+				Method:       deliveries[i].Event.Method,
+				Headers:      deliveries[i].Event.Headers,
+				ContentType:  deliveries[i].Event.ContentType,
+				Body:         &bodyStr,
+				AttemptNum:   1,
+			}
+
+			e.processDelivery(ctx, webhookDB, &deliveries[i], task)
 		}
 	}
 }
 
-// processRetryDelivery handles a single retry delivery triggered by a
-// backoff timer. It loads the delivery and target from the database and
-// re-attempts delivery.
-func (e *Engine) processRetryDelivery(ctx context.Context, req retryRequest) {
-	webhookDB, err := e.dbManager.GetDB(req.webhookID)
-	if err != nil {
-		e.log.Error("failed to get webhook database for retry",
-			"webhook_id", req.webhookID,
-			"delivery_id", req.deliveryID,
-			"error", err,
-		)
-		return
-	}
-
-	var d database.Delivery
-	if err := webhookDB.Preload("Event").
-		First(&d, "id = ?", req.deliveryID).Error; err != nil {
-		e.log.Error("failed to load delivery for retry",
-			"delivery_id", req.deliveryID,
-			"error", err,
-		)
-		return
-	}
-
-	// Verify delivery is still in retrying status (may have been
-	// cancelled or manually resolved while the timer was pending)
-	if d.Status != database.DeliveryStatusRetrying {
-		e.log.Debug("skipping retry for delivery no longer in retrying status",
-			"delivery_id", d.ID,
-			"status", d.Status,
-		)
-		return
-	}
-
-	// Load target from main DB
-	var target database.Target
-	if err := e.database.DB().First(&target, "id = ?", d.TargetID).Error; err != nil {
-		e.log.Error("failed to load target for retry",
-			"delivery_id", d.ID,
-			"target_id", d.TargetID,
-			"error", err,
-		)
-		return
-	}
-	d.Target = target
-
-	e.processDelivery(ctx, webhookDB, &d)
-}
-
 // scheduleRetry creates a Go timer that fires after the given delay and
-// sends a retry request to the engine's retry channel. This is the
-// mechanism for exponential backoff — no periodic DB scanning needed.
-func (e *Engine) scheduleRetry(webhookID, deliveryID string, delay time.Duration) {
+// sends the full DeliveryTask to the engine's retry channel. The task
+// carries all data needed for the retry attempt, so when it fires, the
+// engine can deliver without reading event or target data from the DB.
+func (e *Engine) scheduleRetry(task DeliveryTask, delay time.Duration) {
 	e.log.Debug("scheduling delivery retry",
-		"webhook_id", webhookID,
-		"delivery_id", deliveryID,
+		"webhook_id", task.WebhookID,
+		"delivery_id", task.DeliveryID,
 		"delay", delay,
+		"next_attempt", task.AttemptNum,
 	)
 
 	time.AfterFunc(delay, func() {
 		select {
-		case e.retryCh <- retryRequest{
-			webhookID:  webhookID,
-			deliveryID: deliveryID,
-		}:
+		case e.retryCh <- task:
 		default:
 			e.log.Warn("retry channel full, delivery will be recovered on restart",
-				"delivery_id", deliveryID,
+				"delivery_id", task.DeliveryID,
 			)
 		}
 	})
 }
 
-func (e *Engine) processDelivery(ctx context.Context, webhookDB *gorm.DB, d *database.Delivery) {
+func (e *Engine) processDelivery(ctx context.Context, webhookDB *gorm.DB, d *database.Delivery, task *DeliveryTask) {
 	switch d.Target.Type {
 	case database.TargetTypeHTTP:
 		e.deliverHTTP(ctx, webhookDB, d)
 	case database.TargetTypeRetry:
-		e.deliverRetry(ctx, webhookDB, d)
+		e.deliverRetry(ctx, webhookDB, d, task)
 	case database.TargetTypeDatabase:
 		e.deliverDatabase(webhookDB, d)
 	case database.TargetTypeLog:
@@ -580,22 +671,19 @@ func (e *Engine) deliverHTTP(_ context.Context, webhookDB *gorm.DB, d *database.
 	}
 }
 
-func (e *Engine) deliverRetry(_ context.Context, webhookDB *gorm.DB, d *database.Delivery) {
+func (e *Engine) deliverRetry(_ context.Context, webhookDB *gorm.DB, d *database.Delivery, task *DeliveryTask) {
 	cfg, err := e.parseHTTPConfig(d.Target.Config)
 	if err != nil {
 		e.log.Error("invalid retry target config",
 			"target_id", d.TargetID,
 			"error", err,
 		)
-		e.recordResult(webhookDB, d, 1, false, 0, "", err.Error(), 0)
+		e.recordResult(webhookDB, d, task.AttemptNum, false, 0, "", err.Error(), 0)
 		e.updateDeliveryStatus(webhookDB, d, database.DeliveryStatusFailed)
 		return
 	}
 
-	// Determine attempt number from existing results (in per-webhook DB)
-	var resultCount int64
-	webhookDB.Model(&database.DeliveryResult{}).Where("delivery_id = ?", d.ID).Count(&resultCount)
-	attemptNum := int(resultCount) + 1
+	attemptNum := task.AttemptNum
 
 	// Attempt delivery immediately — backoff is handled by the timer
 	// that triggered this call, not by polling.
@@ -625,14 +713,17 @@ func (e *Engine) deliverRetry(_ context.Context, webhookDB *gorm.DB, d *database
 		e.updateDeliveryStatus(webhookDB, d, database.DeliveryStatusRetrying)
 
 		// Schedule a timer for the next retry with exponential backoff.
-		// The timer will fire and send a retryRequest to the engine's
-		// retry channel, which triggers processRetryDelivery.
+		// The timer fires a DeliveryTask into the retry channel carrying
+		// all data needed for the next attempt.
 		shift := attemptNum - 1
 		if shift > 30 {
 			shift = 30
 		}
 		backoff := time.Duration(1<<uint(shift)) * time.Second //nolint:gosec // bounded above
-		e.scheduleRetry(d.Event.WebhookID, d.ID, backoff)
+
+		retryTask := *task
+		retryTask.AttemptNum = attemptNum + 1
+		e.scheduleRetry(retryTask, backoff)
 	}
 }
 

internal/handlers/handlers_test.go

@@ -22,7 +22,7 @@ import (
 // noopNotifier is a no-op delivery.Notifier for tests.
 type noopNotifier struct{}
 
-func (n *noopNotifier) Notify(delivery.Notification) {}
+func (n *noopNotifier) Notify([]delivery.DeliveryTask) {}
 
 func TestHandleIndex(t *testing.T) {
 	var h *Handlers

internal/handlers/webhook.go

@@ -17,7 +17,9 @@ const (
 
 // HandleWebhook handles incoming webhook requests at entrypoint URLs.
 // Only POST requests are accepted; all other methods return 405 Method Not Allowed.
-// Events and deliveries are stored in the per-webhook database.
+// Events and deliveries are stored in the per-webhook database. The handler
+// builds self-contained DeliveryTask structs with all target and event data
+// so the delivery engine can process them without additional DB reads.
 func (h *Handlers) HandleWebhook() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodPost {
@@ -116,7 +118,16 @@ func (h *Handlers) HandleWebhook() http.HandlerFunc {
 			return
 		}
 
-		// Create delivery records for each active target
+		// Prepare body pointer for inline transport (≤16KB bodies are
+		// included in the DeliveryTask so the engine needs no DB read).
+		var bodyPtr *string
+		if len(body) < delivery.MaxInlineBodySize {
+			bodyStr := string(body)
+			bodyPtr = &bodyStr
+		}
+
+		// Create delivery records and build self-contained delivery tasks
+		tasks := make([]delivery.DeliveryTask, 0, len(targets))
 		for i := range targets {
 			dlv := &database.Delivery{
 				EventID:  event.ID,
@@ -132,6 +143,22 @@ func (h *Handlers) HandleWebhook() http.HandlerFunc {
 				http.Error(w, "Internal server error", http.StatusInternalServerError)
 				return
 			}
+
+			tasks = append(tasks, delivery.DeliveryTask{
+				DeliveryID:   dlv.ID,
+				EventID:      event.ID,
+				WebhookID:    entrypoint.WebhookID,
+				TargetID:     targets[i].ID,
+				TargetName:   targets[i].Name,
+				TargetType:   targets[i].Type,
+				TargetConfig: targets[i].Config,
+				MaxRetries:   targets[i].MaxRetries,
+				Method:       event.Method,
+				Headers:      event.Headers,
+				ContentType:  event.ContentType,
+				Body:         bodyPtr,
+				AttemptNum:   1,
+			})
 		}
 
 		if err := tx.Commit().Error; err != nil {
@@ -140,22 +167,14 @@ func (h *Handlers) HandleWebhook() http.HandlerFunc {
 			return
 		}
 
-		// Notify the delivery engine with inline event data so it can
-		// process deliveries immediately without a DB round-trip.
-		// Large bodies (>= 16KB) are left nil to keep channel memory
-		// bounded; the engine fetches them from DB on demand.
-		n := delivery.Notification{
-			WebhookID:   entrypoint.WebhookID,
-			EventID:     event.ID,
-			Method:      event.Method,
-			Headers:     event.Headers,
-			ContentType: event.ContentType,
+		// Notify the delivery engine with self-contained delivery tasks.
+		// Each task carries all target config and event data inline so
+		// the engine can deliver without touching any database (in the
+		// ≤16KB happy path). The engine only writes to the DB to record
+		// delivery results after each attempt.
+		if len(tasks) > 0 {
+			h.notifier.Notify(tasks)
 		}
-		bodyStr := string(body)
-		if len(body) < delivery.MaxInlineBodySize {
-			n.Body = &bodyStr
-		}
-		h.notifier.Notify(n)
 
 		h.log.Info("webhook event created",
 			"event_id", event.ID,