diff --git a/CHANGELOG.md b/CHANGELOG.md
index 73e5429c8a..0097fb829b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changes
+
+- Optimization of mutex usage in cache for reaper [#3286](https://github.com/evstack/ev-node/pull/3286)
+
 ## v1.1.1
 
 ### Changes
diff --git a/block/internal/cache/generic_cache.go b/block/internal/cache/generic_cache.go
index 5e9f5ff4f5..96ee82d8b2 100644
--- a/block/internal/cache/generic_cache.go
+++ b/block/internal/cache/generic_cache.go
@@ -58,6 +58,19 @@ func (c *Cache) isSeen(hash string) bool {
 	return c.hashes[hash]
 }
 
+// areSeen checks which hashes have been seen. Returns a boolean slice
+// parallel to the input where result[i] is true if hashes[i] is in the
+// cache. Acquires the read lock once for the entire batch.
+func (c *Cache) areSeen(hashes []string) []bool {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	result := make([]bool, len(hashes))
+	for i, h := range hashes {
+		result[i] = c.hashes[h]
+	}
+	return result
+}
+
 func (c *Cache) setSeen(hash string, height uint64) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -75,6 +88,31 @@ func (c *Cache) removeSeen(hash string) {
 	delete(c.hashes, hash)
 }
 
+// setSeenBatch marks all hashes as seen under a single write lock.
+// For height 0 (transactions), the hashByHeight bookkeeping is skipped
+// since all txs share the same sentinel height — the map lookup and
+// overwrite on every entry is pure overhead with no benefit.
+func (c *Cache) setSeenBatch(hashes []string, height uint64) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if height == 0 {
+		for _, h := range hashes {
+			c.hashes[h] = true
+		}
+		return
+	}
+
+	// currently not used, but there for compleness against setSeen
+	for _, h := range hashes {
+		if existing, ok := c.hashByHeight[height]; ok && existing == h {
+			c.hashes[existing] = true
+			continue
+		}
+		c.hashes[h] = true
+		c.hashByHeight[height] = h
+	}
+}
+
 func (c *Cache) getDAIncluded(hash string) (uint64, bool) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
diff --git a/block/internal/cache/manager.go b/block/internal/cache/manager.go
index a91b1410d7..e907002600 100644
--- a/block/internal/cache/manager.go
+++ b/block/internal/cache/manager.go
@@ -52,6 +52,7 @@ type CacheManager interface {
 
 	// Transaction operations
 	IsTxSeen(hash string) bool
+	AreTxsSeen(hashes []string) []bool
 	SetTxSeen(hash string)
 	SetTxsSeen(hashes []string)
 	CleanupOldTxs(olderThan time.Duration) int
@@ -204,6 +205,10 @@ func (m *implementation) IsTxSeen(hash string) bool {
 	return m.txCache.isSeen(hash)
 }
 
+func (m *implementation) AreTxsSeen(hashes []string) []bool {
+	return m.txCache.areSeen(hashes)
+}
+
 func (m *implementation) SetTxSeen(hash string) {
 	// Use 0 as height since transactions don't have a block height yet
 	m.txCache.setSeen(hash, 0)
@@ -212,9 +217,9 @@ func (m *implementation) SetTxSeen(hash string) {
 }
 
 func (m *implementation) SetTxsSeen(hashes []string) {
+	m.txCache.setSeenBatch(hashes, 0)
 	now := time.Now()
 	for _, hash := range hashes {
-		m.txCache.setSeen(hash, 0)
 		m.txTimestamps.Store(hash, now)
 	}
 }
diff --git a/block/internal/reaping/reaper.go b/block/internal/reaping/reaper.go
index 796505e462..d35dbfff3e 100644
--- a/block/internal/reaping/reaper.go
+++ b/block/internal/reaping/reaper.go
@@ -143,11 +143,6 @@ func (r *Reaper) Stop() error {
 	return nil
 }
 
-type pendingTx struct {
-	tx   []byte
-	hash string
-}
-
 func (r *Reaper) drainMempool(cleanupCh <-chan time.Time) (bool, error) {
 	var totalSubmitted int
 
@@ -175,16 +170,32 @@ func (r *Reaper) drainMempool(cleanupCh <-chan time.Time) (bool, error) {
 			break
 		}
 
-		filtered := r.filterNewTxs(txs)
-		if len(filtered) == 0 {
+		hashes := hashTxs(txs)
+		seen := r.cache.AreTxsSeen(hashes)
+
+		newTxs := make([][]byte, 0, len(txs))
+		newHashes := make([]string, 0, len(txs))
+		for i, tx := range txs {
+			if !seen[i] {
+				newTxs = append(newTxs, tx)
+				newHashes = append(newHashes, hashes[i])
+			}
+		}
+
+		if len(newTxs) == 0 {
 			break
 		}
 
-		n, err := r.submitFiltered(filtered)
+		_, err = r.sequencer.SubmitBatchTxs(r.ctx, coresequencer.SubmitBatchTxsRequest{
+			Id:    []byte(r.chainID),
+			Batch: &coresequencer.Batch{Transactions: newTxs},
+		})
 		if err != nil {
-			return totalSubmitted > 0, err
+			return totalSubmitted > 0, fmt.Errorf("failed to submit txs to sequencer: %w", err)
 		}
-		totalSubmitted += n
+
+		r.cache.SetTxsSeen(newHashes)
+		totalSubmitted += len(newTxs)
 	}
 
 	if totalSubmitted > 0 {
@@ -194,38 +205,16 @@ func (r *Reaper) drainMempool(cleanupCh <-chan time.Time) (bool, error) {
 	return totalSubmitted > 0, nil
 }
 
-func (r *Reaper) filterNewTxs(txs [][]byte) []pendingTx {
-	pending := make([]pendingTx, 0, len(txs))
-	for _, tx := range txs {
-		h := hashTx(tx)
-		if !r.cache.IsTxSeen(h) {
-			pending = append(pending, pendingTx{tx: tx, hash: h})
-		}
-	}
-	return pending
-}
-
-func (r *Reaper) submitFiltered(batch []pendingTx) (int, error) {
-	txs := make([][]byte, len(batch))
-	hashes := make([]string, len(batch))
-	for i, p := range batch {
-		txs[i] = p.tx
-		hashes[i] = p.hash
+func hashTxs(txs [][]byte) []string {
+	hashes := make([]string, len(txs))
+	for i, tx := range txs {
+		h := sha256.Sum256(tx)
+		hashes[i] = hex.EncodeToString(h[:])
 	}
-
-	_, err := r.sequencer.SubmitBatchTxs(r.ctx, coresequencer.SubmitBatchTxsRequest{
-		Id:    []byte(r.chainID),
-		Batch: &coresequencer.Batch{Transactions: txs},
-	})
-	if err != nil {
-		return 0, fmt.Errorf("failed to submit txs to sequencer: %w", err)
-	}
-
-	r.cache.SetTxsSeen(hashes)
-	return len(txs), nil
+	return hashes
 }
 
 func hashTx(tx []byte) string {
-	hash := sha256.Sum256(tx)
-	return hex.EncodeToString(hash[:])
+	h := sha256.Sum256(tx)
+	return hex.EncodeToString(h[:])
 }