diff --git a/quic/api/QuicTransportFunctions.cpp b/quic/api/QuicTransportFunctions.cpp
index 7d1e7a3af..d1f364a57 100644
--- a/quic/api/QuicTransportFunctions.cpp
+++ b/quic/api/QuicTransportFunctions.cpp
@@ -181,6 +181,98 @@ uint64_t writeQuicDataToSocketImpl(
   return written;
 }
 
+DataPathResult continuousMemoryBuildScheduleEncrypt(
+    QuicConnectionStateBase& connection,
+    PacketHeader header,
+    PacketNumberSpace pnSpace,
+    PacketNum packetNum,
+    uint64_t cipherOverhead,
+    QuicPacketScheduler& scheduler,
+    uint64_t writableBytes,
+    IOBufQuicBatch& ioBufBatch,
+    const Aead& aead,
+    const PacketNumberCipher& headerCipher) {
+  auto buf = connection.bufAccessor->obtain();
+  auto prevSize = buf->length();
+  connection.bufAccessor->release(std::move(buf));
+
+  auto rollbackBuf = [&]() {
+    auto buf = connection.bufAccessor->obtain();
+    buf->trimEnd(buf->length() - prevSize);
+    connection.bufAccessor->release(std::move(buf));
+  };
+
+  // It's the scheduler's job to invoke encode header
+  InplaceQuicPacketBuilder pktBuilder(
+      *connection.bufAccessor,
+      connection.udpSendPacketLen,
+      std::move(header),
+      getAckState(connection, pnSpace).largestAckedByPeer);
+  pktBuilder.setCipherOverhead(cipherOverhead);
+  CHECK(scheduler.hasData());
+  auto result =
+      scheduler.scheduleFramesForPacket(std::move(pktBuilder), writableBytes);
+  CHECK(connection.bufAccessor->ownsBuffer());
+  auto& packet = result.packet;
+  if (!packet || packet->packet.frames.empty()) {
+    rollbackBuf();
+    ioBufBatch.flush();
+    if (connection.loopDetectorCallback) {
+      connection.writeDebugState.noWriteReason = NoWriteReason::NO_FRAME;
+    }
+    return DataPathResult::makeBuildFailure();
+  }
+  if (!packet->body) {
+    // No more space remaining.
+    rollbackBuf();
+    ioBufBatch.flush();
+    if (connection.loopDetectorCallback) {
+      connection.writeDebugState.noWriteReason = NoWriteReason::NO_BODY;
+    }
+    return DataPathResult::makeBuildFailure();
+  }
+  CHECK(!packet->header->isChained());
+  auto headerLen = packet->header->length();
+  buf = connection.bufAccessor->obtain();
+  CHECK(
+      packet->body->data() > buf->data() &&
+      packet->body->tail() <= buf->tail());
+  CHECK(
+      packet->header->data() >= buf->data() &&
+      packet->header->tail() < buf->tail());
+  // Trim off everything before the current packet, and the header length, so
+  // buf's data starts from the body part of buf.
+  buf->trimStart(prevSize + headerLen);
+  // buf and packetBuf is actually the same.
+  auto packetBuf =
+      aead.inplaceEncrypt(std::move(buf), packet->header.get(), packetNum);
+  CHECK(packetBuf->headroom() == headerLen + prevSize);
+  // Include header back.
+  packetBuf->prepend(headerLen);
+
+  HeaderForm headerForm = packet->packet.header.getHeaderForm();
+  encryptPacketHeader(
+      headerForm,
+      packetBuf->writableData(),
+      headerLen,
+      packetBuf->data() + headerLen,
+      packetBuf->length() - headerLen,
+      headerCipher);
+  CHECK(!packetBuf->isChained());
+  auto encodedSize = packetBuf->length();
+  // Include previous packets back.
+  packetBuf->prepend(prevSize);
+  connection.bufAccessor->release(std::move(packetBuf));
+  // TODO: I think we should add an API that doesn't need a buffer.
+  bool ret = ioBufBatch.write(nullptr /* no need to pass buf */, encodedSize);
+  // update stats and connection
+  if (ret) {
+    QUIC_STATS(connection.statsCallback, onWrite, encodedSize);
+    QUIC_STATS(connection.statsCallback, onPacketSent);
+  }
+  return DataPathResult::makeWriteResult(ret, std::move(result), encodedSize);
+}
+
 DataPathResult iobufChainBasedBuildScheduleEncrypt(
     QuicConnectionStateBase& connection,
     PacketHeader header,
@@ -1046,7 +1138,10 @@ uint64_t writeConnectionDataToSocket(
     }
 
     // TODO: Select a different DataPathFunc based on TransportSettings
-    const auto& dataPlainFunc = iobufChainBasedBuildScheduleEncrypt;
+    const auto& dataPlainFunc =
+        connection.transportSettings.dataPathType == DataPathType::ChainedMemory
+        ? iobufChainBasedBuildScheduleEncrypt
+        : continuousMemoryBuildScheduleEncrypt;
     auto ret = dataPlainFunc(
         connection,
         std::move(header),
@@ -1088,6 +1183,13 @@ uint64_t writeConnectionDataToSocket(
   }
 
   ioBufBatch.flush();
+  if (connection.transportSettings.dataPathType ==
+      DataPathType::ContinuousMemory) {
+    CHECK(connection.bufAccessor->ownsBuffer());
+    auto buf = connection.bufAccessor->obtain();
+    CHECK(buf->length() == 0 && buf->headroom() == 0);
+    connection.bufAccessor->release(std::move(buf));
+  }
   return ioBufBatch.getPktSent();
 }
 
diff --git a/quic/api/test/QuicTransportFunctionsTest.cpp b/quic/api/test/QuicTransportFunctionsTest.cpp
index d63e460ef..4387f8c4a 100644
--- a/quic/api/test/QuicTransportFunctionsTest.cpp
+++ b/quic/api/test/QuicTransportFunctionsTest.cpp
@@ -2221,5 +2221,258 @@ TEST_F(QuicTransportFunctionsTest, ProbeWriteNewFunctionalFrames) {
       conn->outstandingPackets[1].packet.frames[0].type());
 }
 
+TEST_F(QuicTransportFunctionsTest, WriteWithInplaceBuilder) {
+  auto conn = createConn();
+  conn->transportSettings.dataPathType = DataPathType::ContinuousMemory;
+  auto simpleBufAccessor =
+      std::make_unique<SimpleBufAccessor>(conn->udpSendPacketLen * 16);
+  auto outputBuf = simpleBufAccessor->obtain();
+  auto bufPtr = outputBuf.get();
+  simpleBufAccessor->release(std::move(outputBuf));
+  conn->bufAccessor = simpleBufAccessor.get();
+  conn->transportSettings.batchingMode = QuicBatchingMode::BATCHING_MODE_GSO;
+  EventBase evb;
+  folly::test::MockAsyncUDPSocket mockSock(&evb);
+  EXPECT_CALL(mockSock, getGSO()).WillRepeatedly(Return(true));
+  auto stream = conn->streamManager->createNextBidirectionalStream().value();
+  auto buf = folly::IOBuf::copyBuffer("Andante in C minor");
+  writeDataToQuicStream(*stream, buf->clone(), true);
+  EXPECT_CALL(mockSock, write(_, _))
+      .Times(1)
+      .WillOnce(Invoke([&](const SocketAddress&,
+                           const std::unique_ptr<folly::IOBuf>& sockBuf) {
+        EXPECT_GT(bufPtr->length(), 0);
+        EXPECT_GE(sockBuf->length(), buf->length());
+        EXPECT_EQ(sockBuf.get(), bufPtr);
+        EXPECT_TRUE(folly::IOBufEqualTo()(*sockBuf, *bufPtr));
+        EXPECT_FALSE(sockBuf->isChained());
+        return sockBuf->computeChainDataLength();
+      }));
+  writeQuicDataToSocket(
+      mockSock,
+      *conn,
+      *conn->clientConnectionId,
+      *conn->serverConnectionId,
+      *aead,
+      *headerCipher,
+      getVersion(*conn),
+      conn->transportSettings.writeConnectionDataPacketsLimit);
+  EXPECT_EQ(0, bufPtr->length());
+  EXPECT_EQ(0, bufPtr->headroom());
+}
+
+TEST_F(QuicTransportFunctionsTest, WriteWithInplaceBuilderRollbackBuf) {
+  auto conn = createConn();
+  conn->transportSettings.dataPathType = DataPathType::ContinuousMemory;
+  auto simpleBufAccessor =
+      std::make_unique<SimpleBufAccessor>(conn->udpSendPacketLen * 16);
+  auto outputBuf = simpleBufAccessor->obtain();
+  auto bufPtr = outputBuf.get();
+  simpleBufAccessor->release(std::move(outputBuf));
+  conn->bufAccessor = simpleBufAccessor.get();
+  conn->transportSettings.batchingMode = QuicBatchingMode::BATCHING_MODE_GSO;
+  EventBase evb;
+  folly::test::MockAsyncUDPSocket mockSock(&evb);
+  EXPECT_CALL(mockSock, getGSO()).WillRepeatedly(Return(true));
+  EXPECT_CALL(mockSock, write(_, _)).Times(0);
+  writeQuicDataToSocket(
+      mockSock,
+      *conn,
+      *conn->clientConnectionId,
+      *conn->serverConnectionId,
+      *aead,
+      *headerCipher,
+      getVersion(*conn),
+      conn->transportSettings.writeConnectionDataPacketsLimit);
+  EXPECT_EQ(0, bufPtr->length());
+  EXPECT_EQ(0, bufPtr->headroom());
+}
+
+TEST_F(QuicTransportFunctionsTest, WriteWithInplaceBuilderGSOMultiplePackets) {
+  auto conn = createConn();
+  conn->transportSettings.dataPathType = DataPathType::ContinuousMemory;
+  auto simpleBufAccessor =
+      std::make_unique<SimpleBufAccessor>(conn->udpSendPacketLen * 16);
+  auto outputBuf = simpleBufAccessor->obtain();
+  auto bufPtr = outputBuf.get();
+  simpleBufAccessor->release(std::move(outputBuf));
+  conn->bufAccessor = simpleBufAccessor.get();
+  conn->transportSettings.batchingMode = QuicBatchingMode::BATCHING_MODE_GSO;
+  EventBase evb;
+  folly::test::MockAsyncUDPSocket mockSock(&evb);
+  EXPECT_CALL(mockSock, getGSO()).WillRepeatedly(Return(true));
+  auto stream = conn->streamManager->createNextBidirectionalStream().value();
+  auto buf = buildRandomInputData(conn->udpSendPacketLen * 10);
+  writeDataToQuicStream(*stream, buf->clone(), true);
+  EXPECT_CALL(mockSock, writeGSO(_, _, _))
+      .Times(1)
+      .WillOnce(Invoke([&](const folly::SocketAddress&,
+                           const std::unique_ptr<folly::IOBuf>& sockBuf,
+                           int gso) {
+        EXPECT_LE(gso, conn->udpSendPacketLen);
+        EXPECT_GT(bufPtr->length(), 0);
+        EXPECT_EQ(sockBuf.get(), bufPtr);
+        EXPECT_TRUE(folly::IOBufEqualTo()(*sockBuf, *bufPtr));
+        EXPECT_FALSE(sockBuf->isChained());
+        return sockBuf->length();
+      }));
+  writeQuicDataToSocket(
+      mockSock,
+      *conn,
+      *conn->clientConnectionId,
+      *conn->serverConnectionId,
+      *aead,
+      *headerCipher,
+      getVersion(*conn),
+      conn->transportSettings.writeConnectionDataPacketsLimit);
+  EXPECT_EQ(0, bufPtr->length());
+  EXPECT_EQ(0, bufPtr->headroom());
+}
+
+TEST_F(QuicTransportFunctionsTest, WriteProbingWithInplaceBuilder) {
+  auto conn = createConn();
+  conn->transportSettings.dataPathType = DataPathType::ContinuousMemory;
+  conn->transportSettings.batchingMode = QuicBatchingMode::BATCHING_MODE_GSO;
+  EventBase evb;
+  folly::test::MockAsyncUDPSocket mockSock(&evb);
+  EXPECT_CALL(mockSock, getGSO()).WillRepeatedly(Return(true));
+
+  SimpleBufAccessor bufAccessor(
+      conn->udpSendPacketLen * conn->transportSettings.maxBatchSize);
+  conn->bufAccessor = &bufAccessor;
+  auto buf = bufAccessor.obtain();
+  auto bufPtr = buf.get();
+  bufAccessor.release(std::move(buf));
+
+  auto stream = conn->streamManager->createNextBidirectionalStream().value();
+  auto inputBuf = buildRandomInputData(
+      conn->udpSendPacketLen *
+      conn->transportSettings.writeConnectionDataPacketsLimit);
+  writeDataToQuicStream(*stream, inputBuf->clone(), true);
+  EXPECT_CALL(mockSock, writeGSO(_, _, _))
+      .Times(1)
+      .WillOnce(Invoke([&](const folly::SocketAddress&,
+                           const std::unique_ptr<folly::IOBuf>& sockBuf,
+                           int gso) {
+        EXPECT_LE(gso, conn->udpSendPacketLen);
+        EXPECT_GE(
+            bufPtr->length(),
+            conn->udpSendPacketLen *
+                conn->transportSettings.writeConnectionDataPacketsLimit);
+        EXPECT_EQ(sockBuf.get(), bufPtr);
+        EXPECT_TRUE(folly::IOBufEqualTo()(*sockBuf, *bufPtr));
+        EXPECT_FALSE(sockBuf->isChained());
+        return sockBuf->length();
+      }));
+  writeQuicDataToSocket(
+      mockSock,
+      *conn,
+      *conn->clientConnectionId,
+      *conn->serverConnectionId,
+      *aead,
+      *headerCipher,
+      getVersion(*conn),
+      conn->transportSettings.writeConnectionDataPacketsLimit + 1);
+  ASSERT_EQ(0, bufPtr->length());
+  ASSERT_EQ(0, bufPtr->headroom());
+  EXPECT_GE(conn->outstandingPackets.size(), 5);
+  // Make sure there no more new data to write:
+  StreamFrameScheduler streamScheduler(*conn);
+  ASSERT_FALSE(streamScheduler.hasPendingData());
+
+  // The last packet may not be a full packet
+  auto lastPacketSize = conn->outstandingPackets.back().encodedSize;
+  size_t expectedOutstandingPacketsCount = 5;
+  if (lastPacketSize < conn->udpSendPacketLen) {
+    expectedOutstandingPacketsCount++;
+  }
+  EXPECT_CALL(mockSock, write(_, _))
+      .Times(1)
+      .WillOnce(Invoke([&](const folly::SocketAddress&,
+                           const std::unique_ptr<folly::IOBuf>& buf) {
+        EXPECT_FALSE(buf->isChained());
+        // If the last packet isn't full, it may have the stream length field
+        // but the clone won't have it.
+        EXPECT_LE(buf->length(), lastPacketSize);
+        return buf->length();
+      }));
+  writeProbingDataToSocketForTest(
+      mockSock,
+      *conn,
+      1 /* probesToSend */,
+      *aead,
+      *headerCipher,
+      getVersion(*conn));
+  EXPECT_EQ(
+      conn->outstandingPackets.size(), expectedOutstandingPacketsCount + 1);
+  EXPECT_EQ(0, bufPtr->length());
+  EXPECT_EQ(0, bufPtr->headroom());
+
+  // Clone again, this time 2 pacckets.
+  if (lastPacketSize < conn->udpSendPacketLen) {
+    EXPECT_CALL(mockSock, writeGSO(_, _, _))
+        .Times(1)
+        .WillOnce(Invoke([&](const folly::SocketAddress&,
+                             const std::unique_ptr<folly::IOBuf>& buf,
+                             int gso) {
+          EXPECT_FALSE(buf->isChained());
+          EXPECT_LE(gso, lastPacketSize);
+          EXPECT_LE(buf->length(), lastPacketSize * 2);
+          return buf->length();
+        }));
+  } else {
+    EXPECT_CALL(mockSock, writeGSO(_, _, _))
+        .Times(1)
+        .WillOnce(Invoke([&](const folly::SocketAddress&,
+                             const std::unique_ptr<folly::IOBuf>& buf,
+                             int gso) {
+          EXPECT_FALSE(buf->isChained());
+          EXPECT_EQ(conn->udpSendPacketLen, gso);
+          EXPECT_EQ(buf->length(), conn->udpSendPacketLen * 4);
+          return buf->length();
+        }));
+  }
+  writeProbingDataToSocketForTest(
+      mockSock,
+      *conn,
+      2 /* probesToSend */,
+      *aead,
+      *headerCipher,
+      getVersion(*conn));
+  EXPECT_EQ(0, bufPtr->length());
+  EXPECT_EQ(0, bufPtr->headroom());
+  EXPECT_EQ(
+      conn->outstandingPackets.size(), expectedOutstandingPacketsCount + 3);
+
+  // Clear out all the small packets:
+  while (conn->outstandingPackets.back().encodedSize < conn->udpSendPacketLen) {
+    conn->outstandingPackets.pop_back();
+  }
+  ASSERT_FALSE(conn->outstandingPackets.empty());
+  auto currentOutstandingPackets = conn->outstandingPackets.size();
+
+  // Clone 2 full size packets
+  EXPECT_CALL(mockSock, writeGSO(_, _, _))
+      .Times(1)
+      .WillOnce(Invoke([&](const folly::SocketAddress&,
+                           const std::unique_ptr<folly::IOBuf>& buf,
+                           int gso) {
+        EXPECT_FALSE(buf->isChained());
+        EXPECT_EQ(conn->udpSendPacketLen, gso);
+        EXPECT_EQ(buf->length(), conn->udpSendPacketLen * 2);
+        return buf->length();
+      }));
+  writeProbingDataToSocketForTest(
+      mockSock,
+      *conn,
+      2 /* probesToSend */,
+      *aead,
+      *headerCipher,
+      getVersion(*conn));
+  EXPECT_EQ(conn->outstandingPackets.size(), currentOutstandingPackets + 2);
+  EXPECT_EQ(0, bufPtr->length());
+  EXPECT_EQ(0, bufPtr->headroom());
+}
+
 } // namespace test
 } // namespace quic