diff --git a/stovepipe/extension/storage/BUILD.bazel b/stovepipe/extension/storage/BUILD.bazel
index 801976fb..b4a2c8ac 100644
--- a/stovepipe/extension/storage/BUILD.bazel
+++ b/stovepipe/extension/storage/BUILD.bazel
@@ -3,6 +3,7 @@ load("@rules_go//go:def.bzl", "go_library")
 go_library(
     name = "go_default_library",
     srcs = [
+        "queue_store.go",
         "request_store.go",
         "request_uri_store.go",
         "storage.go",
diff --git a/stovepipe/extension/storage/mock/BUILD.bazel b/stovepipe/extension/storage/mock/BUILD.bazel
index d4058d73..cedba6ea 100644
--- a/stovepipe/extension/storage/mock/BUILD.bazel
+++ b/stovepipe/extension/storage/mock/BUILD.bazel
@@ -3,6 +3,7 @@ load("@rules_go//go:def.bzl", "go_library")
 go_library(
     name = "go_default_library",
     srcs = [
+        "queue_store_mock.go",
         "request_store_mock.go",
         "request_uri_store_mock.go",
         "storage_mock.go",
diff --git a/stovepipe/extension/storage/mock/queue_store_mock.go b/stovepipe/extension/storage/mock/queue_store_mock.go
new file mode 100644
index 00000000..d69e9e9c
--- /dev/null
+++ b/stovepipe/extension/storage/mock/queue_store_mock.go
@@ -0,0 +1,86 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: queue_store.go
+//
+// Generated by this command:
+//
+//	mockgen -source=queue_store.go -destination=mock/queue_store_mock.go -package=mock
+//
+
+// Package mock is a generated GoMock package.
+package mock
+
+import (
+	context "context"
+	reflect "reflect"
+
+	entity "github.com/uber/submitqueue/stovepipe/entity"
+	gomock "go.uber.org/mock/gomock"
+)
+
+// MockQueueStore is a mock of QueueStore interface.
+type MockQueueStore struct {
+	ctrl     *gomock.Controller
+	recorder *MockQueueStoreMockRecorder
+	isgomock struct{}
+}
+
+// MockQueueStoreMockRecorder is the mock recorder for MockQueueStore.
+type MockQueueStoreMockRecorder struct {
+	mock *MockQueueStore
+}
+
+// NewMockQueueStore creates a new mock instance.
+func NewMockQueueStore(ctrl *gomock.Controller) *MockQueueStore {
+	mock := &MockQueueStore{ctrl: ctrl}
+	mock.recorder = &MockQueueStoreMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockQueueStore) EXPECT() *MockQueueStoreMockRecorder {
+	return m.recorder
+}
+
+// Get mocks base method.
+func (m *MockQueueStore) Get(ctx context.Context, name string) (entity.Queue, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Get", ctx, name)
+	ret0, _ := ret[0].(entity.Queue)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Get indicates an expected call of Get.
+func (mr *MockQueueStoreMockRecorder) Get(ctx, name any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Get", reflect.TypeOf((*MockQueueStore)(nil).Get), ctx, name)
+}
+
+// GetOrCreate mocks base method.
+func (m *MockQueueStore) GetOrCreate(ctx context.Context, name string, defaults entity.Queue) (entity.Queue, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "GetOrCreate", ctx, name, defaults)
+	ret0, _ := ret[0].(entity.Queue)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// GetOrCreate indicates an expected call of GetOrCreate.
+func (mr *MockQueueStoreMockRecorder) GetOrCreate(ctx, name, defaults any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetOrCreate", reflect.TypeOf((*MockQueueStore)(nil).GetOrCreate), ctx, name, defaults)
+}
+
+// Update mocks base method.
+func (m *MockQueueStore) Update(ctx context.Context, queue entity.Queue, oldVersion, newVersion int32) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Update", ctx, queue, oldVersion, newVersion)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Update indicates an expected call of Update.
+func (mr *MockQueueStoreMockRecorder) Update(ctx, queue, oldVersion, newVersion any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Update", reflect.TypeOf((*MockQueueStore)(nil).Update), ctx, queue, oldVersion, newVersion)
+}
diff --git a/stovepipe/extension/storage/mock/storage_mock.go b/stovepipe/extension/storage/mock/storage_mock.go
index 7da8ebb9..8e25638b 100644
--- a/stovepipe/extension/storage/mock/storage_mock.go
+++ b/stovepipe/extension/storage/mock/storage_mock.go
@@ -54,6 +54,20 @@ func (mr *MockStorageMockRecorder) Close() *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Close", reflect.TypeOf((*MockStorage)(nil).Close))
 }
 
+// GetQueueStore mocks base method.
+func (m *MockStorage) GetQueueStore() storage.QueueStore {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "GetQueueStore")
+	ret0, _ := ret[0].(storage.QueueStore)
+	return ret0
+}
+
+// GetQueueStore indicates an expected call of GetQueueStore.
+func (mr *MockStorageMockRecorder) GetQueueStore() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetQueueStore", reflect.TypeOf((*MockStorage)(nil).GetQueueStore))
+}
+
 // GetRequestStore mocks base method.
 func (m *MockStorage) GetRequestStore() storage.RequestStore {
 	m.ctrl.T.Helper()
diff --git a/stovepipe/extension/storage/mysql/BUILD.bazel b/stovepipe/extension/storage/mysql/BUILD.bazel
index 28fda8eb..b10bb0ed 100644
--- a/stovepipe/extension/storage/mysql/BUILD.bazel
+++ b/stovepipe/extension/storage/mysql/BUILD.bazel
@@ -3,6 +3,7 @@ load("@rules_go//go:def.bzl", "go_library")
 go_library(
     name = "go_default_library",
     srcs = [
+        "queue_store.go",
         "request_store.go",
         "request_uri_store.go",
         "storage.go",
diff --git a/stovepipe/extension/storage/mysql/queue_store.go b/stovepipe/extension/storage/mysql/queue_store.go
new file mode 100644
index 00000000..223a8374
--- /dev/null
+++ b/stovepipe/extension/storage/mysql/queue_store.go
@@ -0,0 +1,153 @@
+// Copyright (c) 2025 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package mysql
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+
+	"github.com/uber-go/tally"
+	"github.com/uber/submitqueue/platform/metrics"
+	"github.com/uber/submitqueue/stovepipe/entity"
+	"github.com/uber/submitqueue/stovepipe/extension/storage"
+)
+
+type queueStore struct {
+	db    *sql.DB
+	scope tally.Scope
+}
+
+// NewQueueStore creates a new MySQL-backed QueueStore.
+func NewQueueStore(db *sql.DB, scope tally.Scope) storage.QueueStore {
+	return &queueStore{db: db, scope: scope}
+}
+
+// GetOrCreate returns the queue row for name, creating it with defaults if absent.
+func (q *queueStore) GetOrCreate(ctx context.Context, name string, defaults entity.Queue) (ret entity.Queue, retErr error) {
+	op := metrics.Begin(q.scope, "get_or_create")
+	defer func() { op.Complete(retErr) }()
+
+	queue, err := q.Get(ctx, name)
+	if err == nil {
+		return queue, nil
+	}
+	if !storage.IsNotFound(err) {
+		return entity.Queue{}, err
+	}
+
+	toCreate := defaults
+	toCreate.Name = name
+	if toCreate.Version == 0 {
+		toCreate.Version = 1
+	}
+
+	if err := q.create(ctx, toCreate); err != nil {
+		if errors.Is(err, storage.ErrAlreadyExists) {
+			return q.Get(ctx, name)
+		}
+		return entity.Queue{}, err
+	}
+	return toCreate, nil
+}
+
+// Get retrieves a queue by name. Returns ErrNotFound if the queue is not found.
+func (q *queueStore) Get(ctx context.Context, name string) (ret entity.Queue, retErr error) {
+	op := metrics.Begin(q.scope, "get")
+	defer func() { op.Complete(retErr) }()
+
+	var queue entity.Queue
+	err := q.db.QueryRowContext(ctx,
+		"SELECT name, last_green_uri, in_flight_count, latest_request_seq, version FROM queue WHERE name = ?",
+		name,
+	).Scan(
+		&queue.Name,
+		&queue.LastGreenURI,
+		&queue.InFlightCount,
+		&queue.LatestRequestSeq,
+		&queue.Version,
+	)
+
+	if errors.Is(err, sql.ErrNoRows) {
+		return entity.Queue{}, storage.WrapNotFound(err)
+	}
+	if err != nil {
+		return entity.Queue{}, fmt.Errorf("failed to get queue name=%s from the database: %w", name, err)
+	}
+
+	return queue, nil
+}
+
+// Update persists the mutable fields of queue if the stored version matches oldVersion,
+// writing newVersion. Returns ErrVersionMismatch if the stored version does not match.
+func (q *queueStore) Update(ctx context.Context, queue entity.Queue, oldVersion, newVersion int32) (retErr error) {
+	op := metrics.Begin(q.scope, "update")
+	defer func() { op.Complete(retErr) }()
+
+	result, err := q.db.ExecContext(ctx,
+		`UPDATE queue
+		 SET last_green_uri = ?, in_flight_count = ?, latest_request_seq = ?, version = ?
+		 WHERE name = ? AND version = ?`,
+		queue.LastGreenURI,
+		queue.InFlightCount,
+		queue.LatestRequestSeq,
+		newVersion,
+		queue.Name,
+		oldVersion,
+	)
+	if err != nil {
+		return fmt.Errorf(
+			"failed to update queue name=%q oldVersion=%d newVersion=%d: %w",
+			queue.Name, oldVersion, newVersion, err,
+		)
+	}
+
+	rowsAffected, err := result.RowsAffected()
+	if err != nil {
+		return fmt.Errorf(
+			"failed to get rows affected from update for name=%q oldVersion=%d newVersion=%d: %w",
+			queue.Name, oldVersion, newVersion, err,
+		)
+	}
+
+	if rowsAffected != 1 {
+		return fmt.Errorf(
+			"version mismatch for queue update: name=%q expected_version=%d: %w",
+			queue.Name, oldVersion, storage.ErrVersionMismatch,
+		)
+	}
+
+	return nil
+}
+
+func (q *queueStore) create(ctx context.Context, queue entity.Queue) error {
+	_, err := q.db.ExecContext(ctx,
+		`INSERT INTO queue (name, last_green_uri, in_flight_count, latest_request_seq, version)
+		 VALUES (?, ?, ?, ?, ?)`,
+		queue.Name,
+		queue.LastGreenURI,
+		queue.InFlightCount,
+		queue.LatestRequestSeq,
+		queue.Version,
+	)
+	if err != nil {
+		if isDuplicateEntry(err) {
+			return fmt.Errorf("queue name=%s: %w", queue.Name, storage.ErrAlreadyExists)
+		}
+		return fmt.Errorf("failed to insert queue name=%s: %w", queue.Name, err)
+	}
+	return nil
+}
diff --git a/stovepipe/extension/storage/mysql/schema/queue.sql b/stovepipe/extension/storage/mysql/schema/queue.sql
new file mode 100644
index 00000000..9fbd49be
--- /dev/null
+++ b/stovepipe/extension/storage/mysql/schema/queue.sql
@@ -0,0 +1,10 @@
+-- queue holds per-queue coordination state for the validation pipeline: the last-green
+-- bookmark, in-flight gate count, and latest-request sequence pointer.
+CREATE TABLE IF NOT EXISTS queue (
+    name               VARCHAR(255) NOT NULL,
+    last_green_uri     VARCHAR(255) NOT NULL DEFAULT '',
+    in_flight_count    INT          NOT NULL DEFAULT 0,
+    latest_request_seq BIGINT       NOT NULL DEFAULT 0,
+    version            INT          NOT NULL,
+    PRIMARY KEY (name)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
diff --git a/stovepipe/extension/storage/mysql/storage.go b/stovepipe/extension/storage/mysql/storage.go
index 93b04eb7..19f55299 100644
--- a/stovepipe/extension/storage/mysql/storage.go
+++ b/stovepipe/extension/storage/mysql/storage.go
@@ -19,7 +19,6 @@ import (
 
 	_ "github.com/go-sql-driver/mysql"
 	"github.com/uber-go/tally"
-
 	"github.com/uber/submitqueue/stovepipe/extension/storage"
 )
 
@@ -27,6 +26,7 @@ type mysqlStorage struct {
 	db              *sql.DB
 	requestStore    storage.RequestStore
 	requestURIStore storage.RequestURIStore
+	queueStore      storage.QueueStore
 }
 
 // NewStorage creates a new MySQL-backed storage.
@@ -35,6 +35,7 @@ func NewStorage(db *sql.DB, scope tally.Scope) (storage.Storage, error) {
 		db:              db,
 		requestStore:    NewRequestStore(db, scope.SubScope("request_store")),
 		requestURIStore: NewRequestURIStore(db, scope.SubScope("request_uri_store")),
+		queueStore:      NewQueueStore(db, scope.SubScope("queue_store")),
 	}, nil
 }
 
@@ -48,6 +49,11 @@ func (f *mysqlStorage) GetRequestURIStore() storage.RequestURIStore {
 	return f.requestURIStore
 }
 
+// GetQueueStore returns the MySQL-backed QueueStore.
+func (f *mysqlStorage) GetQueueStore() storage.QueueStore {
+	return f.queueStore
+}
+
 // Close closes the underlying database connection.
 func (f *mysqlStorage) Close() error {
 	return f.db.Close()
diff --git a/stovepipe/extension/storage/queue_store.go b/stovepipe/extension/storage/queue_store.go
new file mode 100644
index 00000000..ac12825e
--- /dev/null
+++ b/stovepipe/extension/storage/queue_store.go
@@ -0,0 +1,43 @@
+// Copyright (c) 2025 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package storage
+
+//go:generate mockgen -source=queue_store.go -destination=mock/queue_store_mock.go -package=mock
+
+import (
+	"context"
+
+	"github.com/uber/submitqueue/stovepipe/entity"
+)
+
+// QueueStore persists per-queue coordination rows, keyed by queue name.
+type QueueStore interface {
+	// GetOrCreate returns the queue row for name, creating it with defaults if absent.
+	// defaults supplies initial field values for a new row (Name is set from name).
+	// On a create race, re-reads and returns the canonical row.
+	GetOrCreate(ctx context.Context, name string, defaults entity.Queue) (entity.Queue, error)
+
+	// Get retrieves a queue by name. Returns ErrNotFound if the queue is not found.
+	Get(ctx context.Context, name string) (entity.Queue, error)
+
+	// Update persists the mutable fields of queue if the stored version matches
+	// oldVersion, writing newVersion. Returns ErrVersionMismatch if the stored
+	// version does not match (including when the queue does not exist).
+	//
+	// Version arithmetic is owned by the caller: it computes newVersion (typically
+	// oldVersion+1) and only assigns queue.Version = newVersion after this call
+	// succeeds. The store performs a pure conditional write.
+	Update(ctx context.Context, queue entity.Queue, oldVersion, newVersion int32) error
+}
diff --git a/stovepipe/extension/storage/storage.go b/stovepipe/extension/storage/storage.go
index d42406bb..0d16ea3b 100644
--- a/stovepipe/extension/storage/storage.go
+++ b/stovepipe/extension/storage/storage.go
@@ -50,6 +50,9 @@ type Storage interface {
 	// GetRequestURIStore returns the RequestURIStore instance.
 	GetRequestURIStore() RequestURIStore
 
+	// GetQueueStore returns the QueueStore instance.
+	GetQueueStore() QueueStore
+
 	// Close closes the storage and all underlying connections. Should only be called once at the end of the program.
 	Close() error
 }
diff --git a/test/integration/stovepipe/extension/storage/BUILD.bazel b/test/integration/stovepipe/extension/storage/BUILD.bazel
new file mode 100644
index 00000000..b1f4654b
--- /dev/null
+++ b/test/integration/stovepipe/extension/storage/BUILD.bazel
@@ -0,0 +1,16 @@
+load("@rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["suite.go"],
+    importpath = "github.com/uber/submitqueue/test/integration/stovepipe/extension/storage",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//stovepipe/entity:go_default_library",
+        "//stovepipe/extension/storage:go_default_library",
+        "//test/testutil:go_default_library",
+        "@com_github_stretchr_testify//assert:go_default_library",
+        "@com_github_stretchr_testify//require:go_default_library",
+        "@com_github_stretchr_testify//suite:go_default_library",
+    ],
+)
diff --git a/test/integration/stovepipe/extension/storage/mysql/BUILD.bazel b/test/integration/stovepipe/extension/storage/mysql/BUILD.bazel
index ba1e9e8c..7125598c 100644
--- a/test/integration/stovepipe/extension/storage/mysql/BUILD.bazel
+++ b/test/integration/stovepipe/extension/storage/mysql/BUILD.bazel
@@ -15,6 +15,7 @@ go_test(
         "//stovepipe/entity:go_default_library",
         "//stovepipe/extension/storage:go_default_library",
         "//stovepipe/extension/storage/mysql:go_default_library",
+        "//test/integration/stovepipe/extension/storage:go_default_library",
         "//test/testutil:go_default_library",
         "@com_github_go_sql_driver_mysql//:go_default_library",
         "@com_github_stretchr_testify//require:go_default_library",
diff --git a/test/integration/stovepipe/extension/storage/mysql/storage_test.go b/test/integration/stovepipe/extension/storage/mysql/storage_test.go
index 1efdf7f7..c42b06e8 100644
--- a/test/integration/stovepipe/extension/storage/mysql/storage_test.go
+++ b/test/integration/stovepipe/extension/storage/mysql/storage_test.go
@@ -23,10 +23,10 @@ import (
 	"github.com/stretchr/testify/require"
 	"github.com/stretchr/testify/suite"
 	"github.com/uber-go/tally"
-
 	"github.com/uber/submitqueue/stovepipe/entity"
 	"github.com/uber/submitqueue/stovepipe/extension/storage"
 	mysqlstorage "github.com/uber/submitqueue/stovepipe/extension/storage/mysql"
+	storagesuite "github.com/uber/submitqueue/test/integration/stovepipe/extension/storage"
 	"github.com/uber/submitqueue/test/testutil"
 )
 
@@ -186,3 +186,51 @@ func (s *MySQLRequestStoreSuite) TestURIMappingDistinctAcrossQueues() {
 	require.NoError(s.T(), err)
 	require.Equal(s.T(), "request/queue-b/1", idB)
 }
+
+// MySQLQueueStoreSuite exercises the MySQL-backed QueueStore by embedding the shared contract suite.
+type MySQLQueueStoreSuite struct {
+	storagesuite.QueueStoreContractSuite
+	stack *testutil.ComposeStack
+	db    *sql.DB
+	log   *testutil.TestLogger
+}
+
+func TestMySQLQueueStore(t *testing.T) {
+	suite.Run(t, new(MySQLQueueStoreSuite))
+}
+
+func (s *MySQLQueueStoreSuite) SetupSuite() {
+	t := s.T()
+	ctx := context.Background()
+	s.log = testutil.NewTestLogger(t)
+
+	s.stack = testutil.NewComposeStack(
+		t,
+		s.log,
+		ctx,
+		"docker-compose.yml",
+		"ext-stovepipe-storage-mysql",
+	)
+
+	err := s.stack.Up()
+	require.NoError(t, err, "failed to start compose stack")
+
+	s.db, err = s.stack.ConnectMySQLService("mysql")
+	require.NoError(t, err, "failed to connect to MySQL")
+
+	schemaDir := testutil.SchemaDir("stovepipe/extension/storage/mysql/schema")
+	testutil.ApplySchema(t, s.log, s.db, schemaDir)
+
+	store, err := mysqlstorage.NewStorage(s.db, tally.NoopScope)
+	require.NoError(t, err, "failed to create storage")
+
+	s.SetContext(ctx)
+	s.SetQueueStore(store.GetQueueStore())
+	s.SetLogger(s.log)
+
+	t.Cleanup(func() {
+		if s.db != nil {
+			s.db.Close()
+		}
+	})
+}
diff --git a/test/integration/stovepipe/extension/storage/suite.go b/test/integration/stovepipe/extension/storage/suite.go
new file mode 100644
index 00000000..7c49c5ab
--- /dev/null
+++ b/test/integration/stovepipe/extension/storage/suite.go
@@ -0,0 +1,227 @@
+// Copyright (c) 2025 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package storage
+
+import (
+	"context"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+	"github.com/uber/submitqueue/stovepipe/entity"
+	"github.com/uber/submitqueue/stovepipe/extension/storage"
+	"github.com/uber/submitqueue/test/testutil"
+)
+
+// QueueStoreContractSuite defines contract tests for storage.QueueStore.
+// All QueueStore implementations must pass these tests.
+type QueueStoreContractSuite struct {
+	suite.Suite
+	ctx        context.Context
+	queueStore storage.QueueStore
+	log        *testutil.TestLogger
+}
+
+// SetContext sets the context for tests.
+func (s *QueueStoreContractSuite) SetContext(ctx context.Context) {
+	s.ctx = ctx
+}
+
+// SetQueueStore provides the concrete QueueStore under test.
+func (s *QueueStoreContractSuite) SetQueueStore(store storage.QueueStore) {
+	s.queueStore = store
+}
+
+// SetLogger sets the logger for tests.
+func (s *QueueStoreContractSuite) SetLogger(log *testutil.TestLogger) {
+	s.log = log
+}
+
+func (s *QueueStoreContractSuite) queueDefaults() entity.Queue {
+	return entity.Queue{Version: 1}
+}
+
+// TestQueueStore_GetOrCreateCreates verifies GetOrCreate inserts a new row with zero-value runtime fields.
+func (s *QueueStoreContractSuite) TestQueueStore_GetOrCreateCreates() {
+	t := s.T()
+	const name = "contract/create"
+
+	got, err := s.queueStore.GetOrCreate(s.ctx, name, s.queueDefaults())
+	require.NoError(t, err)
+	assert.Equal(t, entity.Queue{
+		Name:             name,
+		LatestRequestSeq: 0,
+		Version:          1,
+	}, got)
+
+	s.log.Logf("GetOrCreateCreates passed: created queue %s", name)
+}
+
+// TestQueueStore_GetOrCreateWithDefaults verifies caller-supplied defaults are persisted on create.
+func (s *QueueStoreContractSuite) TestQueueStore_GetOrCreateWithDefaults() {
+	t := s.T()
+	const name = "contract/defaults"
+
+	defaults := entity.Queue{
+		LastGreenURI:     "git://remote/monorepo/main/green-bbbb",
+		LatestRequestSeq: 99,
+		Version:          1,
+	}
+
+	got, err := s.queueStore.GetOrCreate(s.ctx, name, defaults)
+	require.NoError(t, err)
+	assert.Equal(t, entity.Queue{
+		Name:             name,
+		LastGreenURI:     defaults.LastGreenURI,
+		LatestRequestSeq: defaults.LatestRequestSeq,
+		Version:          1,
+	}, got)
+
+	s.log.Logf("GetOrCreateWithDefaults passed: persisted defaults for queue %s", name)
+}
+
+// TestQueueStore_GetOrCreateIdempotent verifies a second GetOrCreate returns the existing row unchanged.
+func (s *QueueStoreContractSuite) TestQueueStore_GetOrCreateIdempotent() {
+	t := s.T()
+	const name = "contract/idempotent"
+
+	first, err := s.queueStore.GetOrCreate(s.ctx, name, s.queueDefaults())
+	require.NoError(t, err)
+
+	second, err := s.queueStore.GetOrCreate(s.ctx, name, entity.Queue{
+		LastGreenURI:     "git://remote/monorepo/main/ignored-on-hit",
+		LatestRequestSeq: 500,
+		Version:          1,
+	})
+	require.NoError(t, err)
+	assert.Equal(t, first, second)
+
+	s.log.Logf("GetOrCreateIdempotent passed: queue %s", name)
+}
+
+// TestQueueStore_GetOrCreateDefaultVersion verifies GetOrCreate writes version=1 when defaults.Version is zero.
+func (s *QueueStoreContractSuite) TestQueueStore_GetOrCreateDefaultVersion() {
+	t := s.T()
+	const name = "contract/default-version"
+
+	got, err := s.queueStore.GetOrCreate(s.ctx, name, entity.Queue{})
+	require.NoError(t, err)
+	assert.Equal(t, int32(1), got.Version)
+
+	s.log.Logf("GetOrCreateDefaultVersion passed: queue %s", name)
+}
+
+// TestQueueStore_GetNotFound verifies Get returns ErrNotFound for a missing queue.
+func (s *QueueStoreContractSuite) TestQueueStore_GetNotFound() {
+	t := s.T()
+
+	_, err := s.queueStore.Get(s.ctx, "contract/does-not-exist")
+	assert.True(t, storage.IsNotFound(err))
+
+	s.log.Logf("GetNotFound passed")
+}
+
+// TestQueueStore_UpdateCAS verifies a conditional update persists all mutable fields and rejects stale versions.
+func (s *QueueStoreContractSuite) TestQueueStore_UpdateCAS() {
+	t := s.T()
+	const name = "contract/update-cas"
+
+	created, err := s.queueStore.GetOrCreate(s.ctx, name, s.queueDefaults())
+	require.NoError(t, err)
+
+	updated := created
+	updated.LastGreenURI = "git://remote/monorepo/main/green-cccc"
+	updated.LatestRequestSeq = 42
+	updated.InFlightCount = 1
+	require.NoError(t, s.queueStore.Update(s.ctx, updated, 1, 2))
+
+	got, err := s.queueStore.Get(s.ctx, name)
+	require.NoError(t, err)
+	assert.Equal(t, updated.LastGreenURI, got.LastGreenURI)
+	assert.Equal(t, int64(42), got.LatestRequestSeq)
+	assert.Equal(t, int32(1), got.InFlightCount)
+	assert.Equal(t, int32(2), got.Version)
+
+	err = s.queueStore.Update(s.ctx, updated, 1, 2)
+	assert.ErrorIs(t, err, storage.ErrVersionMismatch)
+
+	s.log.Logf("UpdateCAS passed: queue %s", name)
+}
+
+// TestQueueStore_UpdateNotFoundIsVersionMismatch verifies Update on a missing row returns ErrVersionMismatch.
+func (s *QueueStoreContractSuite) TestQueueStore_UpdateNotFoundIsVersionMismatch() {
+	t := s.T()
+
+	err := s.queueStore.Update(s.ctx, entity.Queue{Name: "contract/missing"}, 1, 2)
+	assert.ErrorIs(t, err, storage.ErrVersionMismatch)
+
+	s.log.Logf("UpdateNotFoundIsVersionMismatch passed")
+}
+
+// TestQueueStore_UpdateSequentialCAS verifies successive conditional updates advance version monotonically.
+func (s *QueueStoreContractSuite) TestQueueStore_UpdateSequentialCAS() {
+	t := s.T()
+	const name = "contract/sequential-cas"
+
+	created, err := s.queueStore.GetOrCreate(s.ctx, name, s.queueDefaults())
+	require.NoError(t, err)
+	require.Equal(t, int32(1), created.Version)
+
+	v2 := created
+	v2.LatestRequestSeq = 10
+	require.NoError(t, s.queueStore.Update(s.ctx, v2, 1, 2))
+
+	v3 := v2
+	v3.Version = 2
+	v3.InFlightCount = 1
+	require.NoError(t, s.queueStore.Update(s.ctx, v3, 2, 3))
+
+	got, err := s.queueStore.Get(s.ctx, name)
+	require.NoError(t, err)
+	assert.Equal(t, int64(10), got.LatestRequestSeq)
+	assert.Equal(t, int32(1), got.InFlightCount)
+	assert.Equal(t, int32(3), got.Version)
+
+	s.log.Logf("UpdateSequentialCAS passed: queue %s", name)
+}
+
+// TestQueueStore_QueueIsolation verifies updates to one queue do not affect another.
+func (s *QueueStoreContractSuite) TestQueueStore_QueueIsolation() {
+	t := s.T()
+	const (
+		nameA = "contract/isolation-a"
+		nameB = "contract/isolation-b"
+	)
+
+	_, err := s.queueStore.GetOrCreate(s.ctx, nameA, s.queueDefaults())
+	require.NoError(t, err)
+	baseline, err := s.queueStore.GetOrCreate(s.ctx, nameB, s.queueDefaults())
+	require.NoError(t, err)
+
+	updatedA := entity.Queue{
+		Name:             nameA,
+		LastGreenURI:     "git://remote/monorepo/a/green",
+		LatestRequestSeq: 7,
+		InFlightCount:    2,
+		Version:          1,
+	}
+	require.NoError(t, s.queueStore.Update(s.ctx, updatedA, 1, 2))
+
+	gotB, err := s.queueStore.Get(s.ctx, nameB)
+	require.NoError(t, err)
+	assert.Equal(t, baseline, gotB)
+
+	s.log.Logf("QueueIsolation passed: queues %s and %s", nameA, nameB)
+}