diff --git a/CHANGELOG.md b/CHANGELOG.md
index b487b6102166..5d7602c02fb0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -50,6 +50,7 @@ Every module contains its own CHANGELOG.md. Please refer to the module you are i
 ### Improvements
 
 * (genutil) [#21701](https://github.com/cosmos/cosmos-sdk/pull/21701) Improved error messages for genesis validation.
+* (sims)[#21613](https://github.com/cosmos/cosmos-sdk/pull/21613) Add sims2 framework and factory methods for simpler message factories in modules
 
 ### Bug Fixes
 
@@ -58,7 +59,7 @@ Every module contains its own CHANGELOG.md. Please refer to the module you are i
 
 ### API Breaking Changes
 
-* (sims)[#21613](https://github.com/cosmos/cosmos-sdk/pull/21613) Add sims2 framework and factory methods for simpler message factories in modules
+* (types/mempool) [#21744](https://github.com/cosmos/cosmos-sdk/pull/21744) Update types/mempool.Mempool interface to take decoded transactions. This avoid to decode the transaction twice.
 
 ### Deprecated
 
diff --git a/baseapp/abci_utils.go b/baseapp/abci_utils.go
index e7bb5904a7f7..bc0cb9daccdd 100644
--- a/baseapp/abci_utils.go
+++ b/baseapp/abci_utils.go
@@ -264,19 +264,25 @@ func (h *DefaultProposalHandler) PrepareProposalHandler() sdk.PrepareProposalHan
 
 		defer h.txSelector.Clear()
 
+		// decode transactions
+		decodedTxs := make([]sdk.Tx, len(req.Txs))
+		for i, txBz := range req.Txs {
+			tx, err := h.txVerifier.TxDecode(txBz)
+			if err != nil {
+				return nil, err
+			}
+
+			decodedTxs[i] = tx
+		}
+
 		// If the mempool is nil or NoOp we simply return the transactions
 		// requested from CometBFT, which, by default, should be in FIFO order.
 		//
 		// Note, we still need to ensure the transactions returned respect req.MaxTxBytes.
 		_, isNoOp := h.mempool.(mempool.NoOpMempool)
 		if h.mempool == nil || isNoOp {
-			for _, txBz := range req.Txs {
-				tx, err := h.txVerifier.TxDecode(txBz)
-				if err != nil {
-					return nil, err
-				}
-
-				stop := h.txSelector.SelectTxForProposal(ctx, uint64(req.MaxTxBytes), maxBlockGas, tx, txBz)
+			for i, tx := range decodedTxs {
+				stop := h.txSelector.SelectTxForProposal(ctx, uint64(req.MaxTxBytes), maxBlockGas, tx, req.Txs[i])
 				if stop {
 					break
 				}
@@ -291,7 +297,7 @@ func (h *DefaultProposalHandler) PrepareProposalHandler() sdk.PrepareProposalHan
 			selectedTxsNums int
 			invalidTxs      []sdk.Tx // invalid txs to be removed out of the loop to avoid dead lock
 		)
-		h.mempool.SelectBy(ctx, req.Txs, func(memTx sdk.Tx) bool {
+		h.mempool.SelectBy(ctx, decodedTxs, func(memTx sdk.Tx) bool {
 			unorderedTx, ok := memTx.(sdk.TxWithUnordered)
 			isUnordered := ok && unorderedTx.GetUnordered()
 			txSignersSeqs := make(map[string]uint64)
diff --git a/baseapp/abci_utils_test.go b/baseapp/abci_utils_test.go
index 7dae39542c18..e2c88c2431b7 100644
--- a/baseapp/abci_utils_test.go
+++ b/baseapp/abci_utils_test.go
@@ -691,6 +691,7 @@ func (s *ABCIUtilsTestSuite) TestDefaultProposalHandler_PriorityNonceMempoolTxSe
 			ph := baseapp.NewDefaultProposalHandler(mp, app)
 
 			for _, v := range tc.txInputs {
+				app.EXPECT().TxDecode(v.bz).Return(v.tx, nil).AnyTimes()
 				app.EXPECT().PrepareProposalVerifyTx(v.tx).Return(v.bz, nil).AnyTimes()
 				s.NoError(mp.Insert(s.ctx.WithPriority(v.priority), v.tx))
 				tc.req.Txs = append(tc.req.Txs, v.bz)
diff --git a/server/v2/cometbft/abci.go b/server/v2/cometbft/abci.go
index c38bf7fc18cd..dfd113434093 100644
--- a/server/v2/cometbft/abci.go
+++ b/server/v2/cometbft/abci.go
@@ -467,9 +467,10 @@ func (c *Consensus[T]) FinalizeBlock(
 	}
 
 	// remove txs from the mempool
-	err = c.mempool.Remove(decodedTxs)
-	if err != nil {
-		return nil, fmt.Errorf("unable to remove txs: %w", err)
+	for _, tx := range decodedTxs {
+		if err = c.mempool.Remove(tx); err != nil {
+			return nil, fmt.Errorf("unable to remove tx: %w", err)
+		}
 	}
 
 	c.lastCommittedHeight.Store(req.Height)
diff --git a/server/v2/cometbft/handlers/defaults.go b/server/v2/cometbft/handlers/defaults.go
index 18ad38669c9c..d8f43bb2fd25 100644
--- a/server/v2/cometbft/handlers/defaults.go
+++ b/server/v2/cometbft/handlers/defaults.go
@@ -79,7 +79,7 @@ func (h *DefaultProposalHandler[T]) PrepareHandler() PrepareHandler[T] {
 			// check again.
 			_, err := app.ValidateTx(ctx, memTx)
 			if err != nil {
-				err := h.mempool.Remove([]T{memTx})
+				err := h.mempool.Remove(memTx)
 				if err != nil && !errors.Is(err, mempool.ErrTxNotFound) {
 					return nil, err
 				}
diff --git a/server/v2/cometbft/internal/mock/mock_mempool.go b/server/v2/cometbft/internal/mock/mock_mempool.go
index 89d51e955fae..401b12d60139 100644
--- a/server/v2/cometbft/internal/mock/mock_mempool.go
+++ b/server/v2/cometbft/internal/mock/mock_mempool.go
@@ -15,5 +15,6 @@ type MockMempool[T transaction.Tx] struct{}
 
 func (MockMempool[T]) Insert(context.Context, T) error                 { return nil }
 func (MockMempool[T]) Select(context.Context, []T) mempool.Iterator[T] { return nil }
+func (MockMempool[T]) SelectBy(context.Context, []T, func(T) bool)     {}
 func (MockMempool[T]) CountTx() int                                    { return 0 }
-func (MockMempool[T]) Remove([]T) error                                { return nil }
+func (MockMempool[T]) Remove(T) error                                  { return nil }
diff --git a/server/v2/cometbft/mempool/mempool.go b/server/v2/cometbft/mempool/mempool.go
index 3cb81c871508..0b28c5a2b922 100644
--- a/server/v2/cometbft/mempool/mempool.go
+++ b/server/v2/cometbft/mempool/mempool.go
@@ -19,13 +19,18 @@ type Mempool[T transaction.Tx] interface {
 	Insert(context.Context, T) error
 
 	// Select returns an Iterator over the app-side mempool. If txs are specified,
-	// then they shall be incorporated into the Iterator. The Iterator must be
-	// closed by the caller.
+	// then they shall be incorporated into the Iterator. The Iterator is not thread-safe to use.
 	Select(context.Context, []T) Iterator[T]
 
+	// SelectBy use callback to iterate over the mempool, it's thread-safe to use.
+	SelectBy(context.Context, []T, func(T) bool)
+
+	// CountTx returns the number of transactions currently in the mempool.
+	CountTx() int
+
 	// Remove attempts to remove a transaction from the mempool, returning an error
 	// upon failure.
-	Remove([]T) error
+	Remove(T) error
 }
 
 // Iterator defines an app-side mempool iterator interface that is as minimal as
diff --git a/server/v2/cometbft/mempool/noop.go b/server/v2/cometbft/mempool/noop.go
index 86cea55e2c53..25cffcf69979 100644
--- a/server/v2/cometbft/mempool/noop.go
+++ b/server/v2/cometbft/mempool/noop.go
@@ -4,8 +4,11 @@ import (
 	"context"
 
 	"cosmossdk.io/core/transaction"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
+var _ Mempool[sdk.Tx] = (*NoOpMempool[sdk.Tx])(nil) // verify interface at compile time
 var _ Mempool[transaction.Tx] = (*NoOpMempool[transaction.Tx])(nil)
 
 // NoOpMempool defines a no-op mempool. Transactions are completely discarded and
@@ -16,7 +19,8 @@ var _ Mempool[transaction.Tx] = (*NoOpMempool[transaction.Tx])(nil)
 // is FIFO-ordered by default.
 type NoOpMempool[T transaction.Tx] struct{}
 
-func (NoOpMempool[T]) Insert(context.Context, T) error         { return nil }
-func (NoOpMempool[T]) Select(context.Context, []T) Iterator[T] { return nil }
-func (NoOpMempool[T]) CountTx() int                            { return 0 }
-func (NoOpMempool[T]) Remove([]T) error                        { return nil }
+func (NoOpMempool[T]) Insert(context.Context, T) error             { return nil }
+func (NoOpMempool[T]) Select(context.Context, []T) Iterator[T]     { return nil }
+func (NoOpMempool[T]) SelectBy(context.Context, []T, func(T) bool) {}
+func (NoOpMempool[T]) CountTx() int                                { return 0 }
+func (NoOpMempool[T]) Remove(T) error                              { return nil }
diff --git a/simapp/v2/go.mod b/simapp/v2/go.mod
index d25ff700c46b..7998f620d58b 100644
--- a/simapp/v2/go.mod
+++ b/simapp/v2/go.mod
@@ -35,6 +35,7 @@ require (
 	github.com/cosmos/cosmos-db v1.0.3-0.20240911104526-ddc3f09bfc22 // indirect
 	// this version is not used as it is always replaced by the latest Cosmos SDK version
 	github.com/cosmos/cosmos-sdk v0.53.0
+	github.com/spf13/cast v1.7.0 // indirect
 	github.com/spf13/cobra v1.8.1
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.19.0
@@ -194,7 +195,6 @@ require (
 	github.com/sasha-s/go-deadlock v0.3.5 // indirect
 	github.com/sourcegraph/conc v0.3.0 // indirect
 	github.com/spf13/afero v1.11.0 // indirect
-	github.com/spf13/cast v1.7.0 // indirect
 	github.com/subosito/gotenv v1.6.0 // indirect
 	github.com/supranational/blst v0.3.13 // indirect
 	github.com/syndtr/goleveldb v1.0.1-0.20220721030215-126854af5e6d // indirect
diff --git a/simapp/v2/simdv2/cmd/config.go b/simapp/v2/simdv2/cmd/config.go
index ec222cf8846f..51a7adb178e9 100644
--- a/simapp/v2/simdv2/cmd/config.go
+++ b/simapp/v2/simdv2/cmd/config.go
@@ -91,13 +91,11 @@ func initCometConfig() cometbft.CfgOption {
 func initCometOptions[T transaction.Tx]() cometbft.ServerOptions[T] {
 	serverOptions := cometbft.DefaultServerOptions[T]()
 
-	// TODO mempool interface doesn't match!
-
 	// overwrite app mempool, using max-txs option
 	// serverOptions.Mempool = func(cfg map[string]any) mempool.Mempool[T] {
 	// 	if maxTxs := cast.ToInt(cfg[cometbft.FlagMempoolMaxTxs]); maxTxs >= 0 {
-	// 		return mempool.NewSenderNonceMempool(
-	// 			mempool.SenderNonceMaxTxOpt(maxTxs),
+	// 		return sdkmempool.NewSenderNonceMempool(
+	// 			sdkmempool.SenderNonceMaxTxOpt(maxTxs),
 	// 		)
 	// 	}
 
diff --git a/types/mempool/mempool.go b/types/mempool/mempool.go
index 4f8f82f16fa7..6aa29ff3263c 100644
--- a/types/mempool/mempool.go
+++ b/types/mempool/mempool.go
@@ -14,10 +14,10 @@ type Mempool interface {
 
 	// Select returns an Iterator over the app-side mempool. If txs are specified,
 	// then they shall be incorporated into the Iterator. The Iterator is not thread-safe to use.
-	Select(context.Context, [][]byte) Iterator
+	Select(context.Context, []sdk.Tx) Iterator
 
 	// SelectBy use callback to iterate over the mempool, it's thread-safe to use.
-	SelectBy(context.Context, [][]byte, func(sdk.Tx) bool)
+	SelectBy(context.Context, []sdk.Tx, func(sdk.Tx) bool)
 
 	// CountTx returns the number of transactions currently in the mempool.
 	CountTx() int
diff --git a/types/mempool/noop.go b/types/mempool/noop.go
index 33c002080f82..6f9bbf9ae83a 100644
--- a/types/mempool/noop.go
+++ b/types/mempool/noop.go
@@ -17,7 +17,7 @@ var _ Mempool = (*NoOpMempool)(nil)
 type NoOpMempool struct{}
 
 func (NoOpMempool) Insert(context.Context, sdk.Tx) error                  { return nil }
-func (NoOpMempool) Select(context.Context, [][]byte) Iterator             { return nil }
-func (NoOpMempool) SelectBy(context.Context, [][]byte, func(sdk.Tx) bool) {}
+func (NoOpMempool) Select(context.Context, []sdk.Tx) Iterator             { return nil }
+func (NoOpMempool) SelectBy(context.Context, []sdk.Tx, func(sdk.Tx) bool) {}
 func (NoOpMempool) CountTx() int                                          { return 0 }
 func (NoOpMempool) Remove(sdk.Tx) error                                   { return nil }
diff --git a/types/mempool/priority_nonce.go b/types/mempool/priority_nonce.go
index c0f16a16002c..b324801ff5ec 100644
--- a/types/mempool/priority_nonce.go
+++ b/types/mempool/priority_nonce.go
@@ -361,13 +361,13 @@ func (i *PriorityNonceIterator[C]) Tx() sdk.Tx {
 //
 // NOTE: It is not safe to use this iterator while removing transactions from
 // the underlying mempool.
-func (mp *PriorityNonceMempool[C]) Select(ctx context.Context, txs [][]byte) Iterator {
+func (mp *PriorityNonceMempool[C]) Select(ctx context.Context, txs []sdk.Tx) Iterator {
 	mp.mtx.Lock()
 	defer mp.mtx.Unlock()
 	return mp.doSelect(ctx, txs)
 }
 
-func (mp *PriorityNonceMempool[C]) doSelect(_ context.Context, _ [][]byte) Iterator {
+func (mp *PriorityNonceMempool[C]) doSelect(_ context.Context, _ []sdk.Tx) Iterator {
 	if mp.priorityIndex.Len() == 0 {
 		return nil
 	}
@@ -383,7 +383,7 @@ func (mp *PriorityNonceMempool[C]) doSelect(_ context.Context, _ [][]byte) Itera
 }
 
 // SelectBy will hold the mutex during the iteration, callback returns if continue.
-func (mp *PriorityNonceMempool[C]) SelectBy(ctx context.Context, txs [][]byte, callback func(sdk.Tx) bool) {
+func (mp *PriorityNonceMempool[C]) SelectBy(ctx context.Context, txs []sdk.Tx, callback func(sdk.Tx) bool) {
 	mp.mtx.Lock()
 	defer mp.mtx.Unlock()
 
diff --git a/types/mempool/sender_nonce.go b/types/mempool/sender_nonce.go
index f9cb9f200a23..60d1e2991940 100644
--- a/types/mempool/sender_nonce.go
+++ b/types/mempool/sender_nonce.go
@@ -167,13 +167,13 @@ func (snm *SenderNonceMempool) Insert(_ context.Context, tx sdk.Tx) error {
 //
 // NOTE: It is not safe to use this iterator while removing transactions from
 // the underlying mempool.
-func (snm *SenderNonceMempool) Select(ctx context.Context, txs [][]byte) Iterator {
+func (snm *SenderNonceMempool) Select(ctx context.Context, txs []sdk.Tx) Iterator {
 	snm.mtx.Lock()
 	defer snm.mtx.Unlock()
 	return snm.doSelect(ctx, txs)
 }
 
-func (snm *SenderNonceMempool) doSelect(_ context.Context, _ [][]byte) Iterator {
+func (snm *SenderNonceMempool) doSelect(_ context.Context, _ []sdk.Tx) Iterator {
 	var senders []string
 
 	senderCursors := make(map[string]*skiplist.Element)
@@ -202,7 +202,7 @@ func (snm *SenderNonceMempool) doSelect(_ context.Context, _ [][]byte) Iterator
 }
 
 // SelectBy will hold the mutex during the iteration, callback returns if continue.
-func (snm *SenderNonceMempool) SelectBy(ctx context.Context, txs [][]byte, callback func(sdk.Tx) bool) {
+func (snm *SenderNonceMempool) SelectBy(ctx context.Context, txs []sdk.Tx, callback func(sdk.Tx) bool) {
 	snm.mtx.Lock()
 	defer snm.mtx.Unlock()