diff --git a/neo4j.go b/neo4j.go
index 88619d9..ccc8571 100644
--- a/neo4j.go
+++ b/neo4j.go
@@ -25,20 +25,37 @@ func ConnectNeo4j(ctx context.Context, uri, user, password string) (neo4j.Driver
 // the database
 func SetNeo4jSchema(ctx context.Context, driver neo4j.Driver) error {
 	schemaQueries := []string{
-		`CREATE CONSTRAINT user_pubkey IF NOT EXISTS
+		// Constraints
+
+		// User.pubkey
+		`CREATE CONSTRAINT user IF NOT EXISTS
 		 FOR (n:User) REQUIRE n.pubkey IS UNIQUE`,
 
-		`CREATE INDEX user_pubkey IF NOT EXISTS
-		 FOR (n:User) ON (n.pubkey)`,
+		// Relay.url
+		`CREATE CONSTRAINT url IF NOT EXISTS
+		 FOR (n:Relay) REQUIRE n.url IS UNIQUE`,
 
-		`CREATE INDEX event_id IF NOT EXISTS
-		 FOR (n:Event) ON (n.id)`,
+		// Event.id
+		`CREATE CONSTRAINT event IF NOT EXISTS
+		 FOR (n:Event) REQUIRE n.id IS UNIQUE`,
 
+		// Tag.(name, value)
+		`CREATE CONSTRAINT tag IF NOT EXISTS
+		 FOR (n:Tag) REQUIRE (n.name, n.value) IS UNIQUE`,
+
+		// ReplacementKey.(pubkey, kind)
+		`CREATE CONSTRAINT replacement_key IF NOT EXISTS
+		 FOR (n:ReplacementKey) REQUIRE (n.pubkey, n.kind) IS UNIQUE`,
+
+		// Indexes
+
+		// Event.kind
 		`CREATE INDEX event_kind IF NOT EXISTS
 		 FOR (n:Event) ON (n.kind)`,
 
-		`CREATE INDEX tag_name_value IF NOT EXISTS
-		 FOR (n:Tag) ON (n.name, n.value)`,
+		// Event.created_at
+		`CREATE INDEX event_created_at IF NOT EXISTS
+		 FOR (n:Event) ON (n.created_at)`,
 	}
 
 	// Create indexes and constraints
diff --git a/schema.go b/schema.go
index 54d6845..de76989 100644
--- a/schema.go
+++ b/schema.go
@@ -11,10 +11,11 @@ import (
 func NewSimpleMatchKeys() *SimpleMatchKeys {
 	return &SimpleMatchKeys{
 		Keys: map[string][]string{
-			"User":  {"pubkey"},
-			"Relay": {"url"},
-			"Event": {"id"},
-			"Tag":   {"name", "value"},
+			"User":           {"pubkey"},
+			"Relay":          {"url"},
+			"Event":          {"id"},
+			"Tag":            {"name", "value"},
+			"ReplacementKey": {"pubkey", "kind"},
 		},
 	}
 }
@@ -41,6 +42,13 @@ func NewTagNode(name string, value string) *Node {
 		"value": value})
 }
 
+func NewReplacementKeyNode(pubkey string, kind int) *Node {
+	return NewNode("ReplacementKey", Properties{
+		"pubkey": pubkey,
+		"kind":   kind,
+	})
+}
+
 // ========================================
 // Relationship Constructors
 // ========================================
@@ -70,6 +78,30 @@ func NewReferencesUserRel(
 		"REFERENCES", "Tag", "User", start, end, props)
 }
 
+func NewIsReplaceableRel(
+	start *Node, end *Node, props Properties) *Relationship {
+	return NewRelationshipWithValidation(
+		"IS_REPLACEABLE", "Event", "ReplacementKey", start, end, props)
+}
+
+func NewForUserRel(
+	start *Node, end *Node, props Properties) *Relationship {
+	return NewRelationshipWithValidation(
+		"FOR_USER", "ReplacementKey", "User", start, end, props)
+}
+
+func NewWithDTagRel(
+	start *Node, end *Node, props Properties) *Relationship {
+	return NewRelationshipWithValidation(
+		"WITH_D_TAG", "ReplacementKey", "Tag", start, end, props)
+}
+
+func NewReferencesReplacementKeyRel(
+	start *Node, end *Node, props Properties) *Relationship {
+	return NewRelationshipWithValidation(
+		"REFERENCES", "Tag", "ReplacementKey", start, end, props)
+}
+
 // ========================================
 // Relationship Constructor Helpers
 // ========================================