diff --git a/internal/fakechain/fakechain.go b/internal/fakechain/fakechain.go
index 83f889f10..51e3a8a0a 100644
--- a/internal/fakechain/fakechain.go
+++ b/internal/fakechain/fakechain.go
@@ -62,7 +62,7 @@ func NewFakeChainWithCustomCfg(protocolCfg func(c *config.Blockchain)) *FakeChai
 		protocolCfg(&cfg)
 	}
 	return &FakeChain{
-		Pool:           mempool.New(10, 0, false),
+		Pool:           mempool.New(10, 0, false, nil),
 		PoolTxF:        func(*transaction.Transaction) error { return nil },
 		poolTxWithData: func(*transaction.Transaction, any, *mempool.Pool) error { return nil },
 		blocks:         make(map[util.Uint256]*block.Block),
diff --git a/pkg/consensus/consensus.go b/pkg/consensus/consensus.go
index 777f5d341..7cd1e52d0 100644
--- a/pkg/consensus/consensus.go
+++ b/pkg/consensus/consensus.go
@@ -506,7 +506,7 @@ func (s *service) verifyBlock(b block.Block) bool {
 	}
 
 	var fee int64
-	var pool = mempool.New(len(coreb.Transactions), 0, false)
+	var pool = mempool.New(len(coreb.Transactions), 0, false, nil)
 	var mainPool = s.Chain.GetMemPool()
 	for _, tx := range coreb.Transactions {
 		var err error
diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 29dca5738..f1e514f63 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -309,7 +309,7 @@ func NewBlockchain(s storage.Store, cfg config.Blockchain, log *zap.Logger) (*Bl
 		store:       s,
 		stopCh:      make(chan struct{}),
 		runToExitCh: make(chan struct{}),
-		memPool:     mempool.New(cfg.MemPoolSize, 0, false),
+		memPool:     mempool.New(cfg.MemPoolSize, 0, false, updateMempoolMetrics),
 		log:         log,
 		events:      make(chan bcEvent),
 		subCh:       make(chan any),
@@ -1446,7 +1446,7 @@ func (bc *Blockchain) AddBlock(block *block.Block) error {
 		if !block.MerkleRoot.Equals(merkle) {
 			return errors.New("invalid block: MerkleRoot mismatch")
 		}
-		mp = mempool.New(len(block.Transactions), 0, false)
+		mp = mempool.New(len(block.Transactions), 0, false, nil)
 		for _, tx := range block.Transactions {
 			var err error
 			// Transactions are verified before adding them
@@ -2651,7 +2651,7 @@ func (bc *Blockchain) IsTxStillRelevant(t *transaction.Transaction, txpool *memp
 // current blockchain state. Note that this verification is completely isolated
 // from the main node's mempool.
 func (bc *Blockchain) VerifyTx(t *transaction.Transaction) error {
-	var mp = mempool.New(1, 0, false)
+	var mp = mempool.New(1, 0, false, nil)
 	bc.lock.RLock()
 	defer bc.lock.RUnlock()
 	return bc.verifyAndPoolTx(t, mp, bc)
diff --git a/pkg/core/blockchain_neotest_test.go b/pkg/core/blockchain_neotest_test.go
index da59af3cf..ad8c74b5b 100644
--- a/pkg/core/blockchain_neotest_test.go
+++ b/pkg/core/blockchain_neotest_test.go
@@ -1301,7 +1301,7 @@ func TestBlockchain_VerifyTx(t *testing.T) {
 		require.True(t, errors.Is(err, core.ErrAlreadyExists))
 	})
 	t.Run("MemPoolOOM", func(t *testing.T) {
-		mp := mempool.New(1, 0, false)
+		mp := mempool.New(1, 0, false, nil)
 		tx1 := newTestTx(t, h, testScript)
 		tx1.NetworkFee += 10000 // Give it more priority.
 		require.NoError(t, accs[0].SignTx(netmode.UnitTestNet, tx1))
@@ -1860,7 +1860,7 @@ func TestBlockchain_VerifyTx(t *testing.T) {
 			return tx
 		}
 
-		mp := mempool.New(10, 1, false)
+		mp := mempool.New(10, 1, false, nil)
 		verificationF := func(tx *transaction.Transaction, data any) error {
 			if data.(int) > 5 {
 				return errors.New("bad data")
diff --git a/pkg/core/mempool/mem_pool.go b/pkg/core/mempool/mem_pool.go
index 0faf79c96..901b528bb 100644
--- a/pkg/core/mempool/mem_pool.go
+++ b/pkg/core/mempool/mem_pool.go
@@ -65,9 +65,10 @@ type Pool struct {
 	// oracleResp contains the ids of oracle responses for the tx in the pool.
 	oracleResp map[uint64]util.Uint256
 
-	capacity   int
-	feePerByte int64
-	payerIndex int
+	capacity        int
+	feePerByte      int64
+	payerIndex      int
+	updateMetricsCb func(int)
 
 	resendThreshold uint32
 	resendFunc      func(*transaction.Transaction, any)
@@ -286,7 +287,9 @@ func (mp *Pool) Add(t *transaction.Transaction, fee Feer, data ...any) error {
 	// we already checked balance in checkTxConflicts, so don't need to check again
 	mp.tryAddSendersFee(pItem.txn, fee, false)
 
-	updateMempoolMetrics(len(mp.verifiedTxes))
+	if mp.updateMetricsCb != nil {
+		mp.updateMetricsCb(len(mp.verifiedTxes))
+	}
 	mp.lock.Unlock()
 
 	if mp.subscriptionsOn.Load() {
@@ -342,7 +345,9 @@ func (mp *Pool) removeInternal(hash util.Uint256, feer Feer) {
 			}
 		}
 	}
-	updateMempoolMetrics(len(mp.verifiedTxes))
+	if mp.updateMetricsCb != nil {
+		mp.updateMetricsCb(len(mp.verifiedTxes))
+	}
 }
 
 // RemoveStale filters verified transactions through the given function keeping
@@ -420,7 +425,7 @@ func (mp *Pool) checkPolicy(tx *transaction.Transaction, policyChanged bool) boo
 }
 
 // New returns a new Pool struct.
-func New(capacity int, payerIndex int, enableSubscriptions bool) *Pool {
+func New(capacity int, payerIndex int, enableSubscriptions bool, updateMetricsCb func(int)) *Pool {
 	mp := &Pool{
 		verifiedMap:          make(map[util.Uint256]*transaction.Transaction, capacity),
 		verifiedTxes:         make([]item, 0, capacity),
@@ -434,6 +439,7 @@ func New(capacity int, payerIndex int, enableSubscriptions bool) *Pool {
 		events:               make(chan mempoolevent.Event),
 		subCh:                make(chan chan<- mempoolevent.Event),
 		unsubCh:              make(chan chan<- mempoolevent.Event),
+		updateMetricsCb:      updateMetricsCb,
 	}
 	mp.subscriptionsOn.Store(false)
 	return mp
diff --git a/pkg/core/mempool/mem_pool_test.go b/pkg/core/mempool/mem_pool_test.go
index 43a1f0cef..66882e4f3 100644
--- a/pkg/core/mempool/mem_pool_test.go
+++ b/pkg/core/mempool/mem_pool_test.go
@@ -45,7 +45,7 @@ func (fs *FeerStub) P2PSigExtensionsEnabled() bool {
 }
 
 func testMemPoolAddRemoveWithFeer(t *testing.T, fs Feer) {
-	mp := New(10, 0, false)
+	mp := New(10, 0, false, nil)
 	tx := transaction.New([]byte{byte(opcode.PUSH1)}, 0)
 	tx.Nonce = 0
 	tx.Signers = []transaction.Signer{{Account: util.Uint160{1, 2, 3}}}
@@ -66,7 +66,7 @@ func testMemPoolAddRemoveWithFeer(t *testing.T, fs Feer) {
 }
 
 func TestMemPoolRemoveStale(t *testing.T) {
-	mp := New(5, 0, false)
+	mp := New(5, 0, false, nil)
 	txs := make([]*transaction.Transaction, 5)
 	for i := range txs {
 		txs[i] = transaction.New([]byte{byte(opcode.PUSH1)}, 0)
@@ -117,7 +117,7 @@ func TestMemPoolAddRemove(t *testing.T) {
 func TestOverCapacity(t *testing.T) {
 	var fs = &FeerStub{balance: 10000000}
 	const mempoolSize = 10
-	mp := New(mempoolSize, 0, false)
+	mp := New(mempoolSize, 0, false, nil)
 
 	for i := 0; i < mempoolSize; i++ {
 		tx := transaction.New([]byte{byte(opcode.PUSH1)}, 0)
@@ -193,7 +193,7 @@ func TestOverCapacity(t *testing.T) {
 func TestGetVerified(t *testing.T) {
 	var fs = &FeerStub{}
 	const mempoolSize = 10
-	mp := New(mempoolSize, 0, false)
+	mp := New(mempoolSize, 0, false, nil)
 
 	txes := make([]*transaction.Transaction, 0, mempoolSize)
 	for i := 0; i < mempoolSize; i++ {
@@ -217,7 +217,7 @@ func TestGetVerified(t *testing.T) {
 func TestRemoveStale(t *testing.T) {
 	var fs = &FeerStub{}
 	const mempoolSize = 10
-	mp := New(mempoolSize, 0, false)
+	mp := New(mempoolSize, 0, false, nil)
 
 	txes1 := make([]*transaction.Transaction, 0, mempoolSize/2)
 	txes2 := make([]*transaction.Transaction, 0, mempoolSize/2)
@@ -250,7 +250,7 @@ func TestRemoveStale(t *testing.T) {
 }
 
 func TestMemPoolFees(t *testing.T) {
-	mp := New(10, 0, false)
+	mp := New(10, 0, false, nil)
 	fs := &FeerStub{balance: 10000000}
 	sender0 := util.Uint160{1, 2, 3}
 	tx0 := transaction.New([]byte{byte(opcode.PUSH1)}, 0)
@@ -355,7 +355,7 @@ func TestMempoolItemsOrder(t *testing.T) {
 }
 
 func TestMempoolAddRemoveOracleResponse(t *testing.T) {
-	mp := New(3, 0, false)
+	mp := New(3, 0, false, nil)
 	nonce := uint32(0)
 	fs := &FeerStub{balance: 10000}
 	newTx := func(netFee int64, id uint64) *transaction.Transaction {
@@ -425,7 +425,7 @@ func TestMempoolAddRemoveOracleResponse(t *testing.T) {
 
 func TestMempoolAddRemoveConflicts(t *testing.T) {
 	capacity := 6
-	mp := New(capacity, 0, false)
+	mp := New(capacity, 0, false, nil)
 	var (
 		fs           = &FeerStub{p2pSigExt: true, balance: 100000}
 		nonce uint32 = 1
@@ -555,7 +555,7 @@ func TestMempoolAddWithDataGetData(t *testing.T) {
 		blockHeight: 5,
 		balance:     100,
 	}
-	mp := New(10, 1, false)
+	mp := New(10, 1, false, nil)
 	newTx := func(t *testing.T, netFee int64) *transaction.Transaction {
 		tx := transaction.New([]byte{byte(opcode.RET)}, 0)
 		tx.Signers = []transaction.Signer{{}, {}}
diff --git a/pkg/core/mempool/prometheus.go b/pkg/core/mempool/prometheus.go
deleted file mode 100644
index dbe073a0d..000000000
--- a/pkg/core/mempool/prometheus.go
+++ /dev/null
@@ -1,24 +0,0 @@
-package mempool
-
-import "github.com/prometheus/client_golang/prometheus"
-
-var (
-	//mempoolUnsortedTx prometheus metric.
-	mempoolUnsortedTx = prometheus.NewGauge(
-		prometheus.GaugeOpts{
-			Help:      "Mempool Unsorted TXs",
-			Name:      "mempool_unsorted_tx",
-			Namespace: "neogo",
-		},
-	)
-)
-
-func init() {
-	prometheus.MustRegister(
-		mempoolUnsortedTx,
-	)
-}
-
-func updateMempoolMetrics(unsortedTxnLen int) {
-	mempoolUnsortedTx.Set(float64(unsortedTxnLen))
-}
diff --git a/pkg/core/mempool/subscriptions_test.go b/pkg/core/mempool/subscriptions_test.go
index bbe1bc2a3..d476f20bc 100644
--- a/pkg/core/mempool/subscriptions_test.go
+++ b/pkg/core/mempool/subscriptions_test.go
@@ -13,7 +13,7 @@ import (
 
 func TestSubscriptions(t *testing.T) {
 	t.Run("disabled subscriptions", func(t *testing.T) {
-		mp := New(5, 0, false)
+		mp := New(5, 0, false, nil)
 		require.Panics(t, func() {
 			mp.RunSubscriptions()
 		})
@@ -24,7 +24,7 @@ func TestSubscriptions(t *testing.T) {
 
 	t.Run("enabled subscriptions", func(t *testing.T) {
 		fs := &FeerStub{balance: 100}
-		mp := New(2, 0, true)
+		mp := New(2, 0, true, nil)
 		mp.RunSubscriptions()
 		subChan1 := make(chan mempoolevent.Event, 3)
 		subChan2 := make(chan mempoolevent.Event, 3)
diff --git a/pkg/core/prometheus.go b/pkg/core/prometheus.go
index f47b60e20..8e429d044 100644
--- a/pkg/core/prometheus.go
+++ b/pkg/core/prometheus.go
@@ -6,7 +6,7 @@ import (
 
 // Metrics for monitoring service.
 var (
-	//blockHeight prometheus metric.
+	// blockHeight prometheus metric.
 	blockHeight = prometheus.NewGauge(
 		prometheus.GaugeOpts{
 			Help:      "Current index of processed block",
@@ -14,7 +14,7 @@ var (
 			Namespace: "neogo",
 		},
 	)
-	//persistedHeight prometheus metric.
+	// persistedHeight prometheus metric.
 	persistedHeight = prometheus.NewGauge(
 		prometheus.GaugeOpts{
 			Help:      "Current persisted block count",
@@ -22,7 +22,7 @@ var (
 			Namespace: "neogo",
 		},
 	)
-	//headerHeight prometheus metric.
+	// headerHeight prometheus metric.
 	headerHeight = prometheus.NewGauge(
 		prometheus.GaugeOpts{
 			Help:      "Current header height",
@@ -30,6 +30,14 @@ var (
 			Namespace: "neogo",
 		},
 	)
+	// mempoolUnsortedTx prometheus metric.
+	mempoolUnsortedTx = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Help:      "Mempool unsorted transactions",
+			Name:      "mempool_unsorted_tx",
+			Namespace: "neogo",
+		},
+	)
 )
 
 func init() {
@@ -37,6 +45,7 @@ func init() {
 		blockHeight,
 		persistedHeight,
 		headerHeight,
+		mempoolUnsortedTx,
 	)
 }
 
@@ -51,3 +60,8 @@ func updateHeaderHeightMetric(hHeight uint32) {
 func updateBlockHeightMetric(bHeight uint32) {
 	blockHeight.Set(float64(bHeight))
 }
+
+// updateMempoolMetrics updates metric of the number of unsorted txs inside the mempool.
+func updateMempoolMetrics(unsortedTxnLen int) {
+	mempoolUnsortedTx.Set(float64(unsortedTxnLen))
+}
diff --git a/pkg/network/prometheus.go b/pkg/network/prometheus.go
index bc1156afe..483e877f7 100644
--- a/pkg/network/prometheus.go
+++ b/pkg/network/prometheus.go
@@ -50,6 +50,15 @@ var (
 		},
 	)
 	p2pCmds = make(map[CommandType]prometheus.Histogram)
+
+	// notarypoolUnsortedTx prometheus metric.
+	notarypoolUnsortedTx = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Help:      "Notary request pool fallback txs",
+			Name:      "notarypool_unsorted_tx",
+			Namespace: "neogo",
+		},
+	)
 )
 
 func init() {
@@ -59,6 +68,7 @@ func init() {
 		servAndNodeVersion,
 		poolCount,
 		blockQueueLength,
+		notarypoolUnsortedTx,
 	)
 	for _, cmd := range []CommandType{CMDVersion, CMDVerack, CMDGetAddr,
 		CMDAddr, CMDPing, CMDPong, CMDGetHeaders, CMDHeaders, CMDGetBlocks,
@@ -103,3 +113,9 @@ func addCmdTimeMetric(cmd CommandType, t time.Duration) {
 	}
 	p2pCmds[cmd].Observe(t.Seconds())
 }
+
+// updateNotarypoolMetrics updates metric of the number of fallback txs inside
+// the notary request pool.
+func updateNotarypoolMetrics(unsortedTxnLen int) {
+	notarypoolUnsortedTx.Set(float64(unsortedTxnLen))
+}
diff --git a/pkg/network/server.go b/pkg/network/server.go
index b6661b2a4..1cb62d637 100644
--- a/pkg/network/server.go
+++ b/pkg/network/server.go
@@ -198,7 +198,7 @@ func newServerFromConstructors(config ServerConfig, chain Ledger, stSync StateSy
 	}
 	if chain.P2PSigExtensionsEnabled() {
 		s.notaryFeer = NewNotaryFeer(chain)
-		s.notaryRequestPool = mempool.New(s.config.P2PNotaryRequestPayloadPoolSize, 1, true)
+		s.notaryRequestPool = mempool.New(s.config.P2PNotaryRequestPayloadPoolSize, 1, true, updateNotarypoolMetrics)
 		chain.RegisterPostBlock(func(isRelevant func(*transaction.Transaction, *mempool.Pool, bool) bool, txpool *mempool.Pool, _ *block.Block) {
 			s.notaryRequestPool.RemoveStale(func(t *transaction.Transaction) bool {
 				return isRelevant(t, txpool, true)
diff --git a/pkg/services/notary/core_test.go b/pkg/services/notary/core_test.go
index 657a2bc90..638da3887 100644
--- a/pkg/services/notary/core_test.go
+++ b/pkg/services/notary/core_test.go
@@ -47,7 +47,7 @@ func getTestNotary(t *testing.T, bc *core.Blockchain, walletPath, pass string, o
 		Chain:   bc,
 		Log:     zaptest.NewLogger(t),
 	}
-	mp := mempool.New(10, 1, true)
+	mp := mempool.New(10, 1, true, nil)
 	ntr, err := notary.NewNotary(cfg, netmode.UnitTestNet, mp, onTx)
 	require.NoError(t, err)
 
diff --git a/pkg/services/notary/node_test.go b/pkg/services/notary/node_test.go
index b1779cd6c..93c666dc6 100644
--- a/pkg/services/notary/node_test.go
+++ b/pkg/services/notary/node_test.go
@@ -21,7 +21,7 @@ func getTestNotary(t *testing.T, bc Ledger, walletPath, pass string) (*wallet.Ac
 			Password: pass,
 		},
 	}
-	mp := mempool.New(10, 1, true)
+	mp := mempool.New(10, 1, true, nil)
 	cfg := Config{
 		MainCfg: mainCfg,
 		Chain:   bc,
diff --git a/pkg/services/notary/notary_test.go b/pkg/services/notary/notary_test.go
index d3d173e99..9df86c72f 100644
--- a/pkg/services/notary/notary_test.go
+++ b/pkg/services/notary/notary_test.go
@@ -27,21 +27,21 @@ func TestWallet(t *testing.T) {
 	}
 	t.Run("unexisting wallet", func(t *testing.T) {
 		cfg.MainCfg.UnlockWallet.Path = "./testdata/does_not_exists.json"
-		_, err := NewNotary(cfg, netmode.UnitTestNet, mempool.New(1, 1, true), nil)
+		_, err := NewNotary(cfg, netmode.UnitTestNet, mempool.New(1, 1, true, nil), nil)
 		require.Error(t, err)
 	})
 
 	t.Run("bad password", func(t *testing.T) {
 		cfg.MainCfg.UnlockWallet.Path = "./testdata/notary1.json"
 		cfg.MainCfg.UnlockWallet.Password = "invalid"
-		_, err := NewNotary(cfg, netmode.UnitTestNet, mempool.New(1, 1, true), nil)
+		_, err := NewNotary(cfg, netmode.UnitTestNet, mempool.New(1, 1, true, nil), nil)
 		require.Error(t, err)
 	})
 
 	t.Run("good", func(t *testing.T) {
 		cfg.MainCfg.UnlockWallet.Path = "./testdata/notary1.json"
 		cfg.MainCfg.UnlockWallet.Password = "one"
-		_, err := NewNotary(cfg, netmode.UnitTestNet, mempool.New(1, 1, true), nil)
+		_, err := NewNotary(cfg, netmode.UnitTestNet, mempool.New(1, 1, true, nil), nil)
 		require.NoError(t, err)
 	})
 }