diff --git a/src/box/iproto.cc b/src/box/iproto.cc
index f2952812f049f045e332f9b341e1edc8ebe6930c..7ef6c631cb153a2bbda74838874344c006737da1 100644
--- a/src/box/iproto.cc
+++ b/src/box/iproto.cc
@@ -949,7 +949,7 @@ iproto_connection_close(struct iproto_connection *con)
 		 * parsed data is processed.  It's important this
 		 * is done only once.
 		 */
-		con->p_ibuf->wpos -= con->parse_size;
+		ibuf_discard(con->p_ibuf, con->parse_size);
 		mh_int_t node;
 		mh_foreach(con->streams, node) {
 			struct iproto_stream *stream = (struct iproto_stream *)
@@ -1056,15 +1056,16 @@ iproto_connection_input_buffer(struct iproto_connection *con)
 	}
 
 	xibuf_reserve(new_ibuf, to_read + con->parse_size);
-	/*
-	 * Discard unparsed data in the old buffer, otherwise it
-	 * won't be recycled when all parsed requests are processed.
-	 */
-	old_ibuf->wpos -= con->parse_size;
 	if (con->parse_size != 0) {
 		/* Move the cached request prefix to the new buffer. */
-		memcpy(new_ibuf->rpos, old_ibuf->wpos, con->parse_size);
-		new_ibuf->wpos += con->parse_size;
+		void *wpos = ibuf_alloc(new_ibuf, con->parse_size);
+		assert(wpos != NULL);
+		memcpy(wpos, old_ibuf->wpos - con->parse_size, con->parse_size);
+		/*
+		 * Discard unparsed data in the old buffer, otherwise it
+		 * won't be recycled when all parsed requests are processed.
+		 */
+		ibuf_discard(old_ibuf, con->parse_size);
 		/*
 		 * We made ibuf idle. If obuf was already idle it
 		 * makes the both ibuf and obuf idle, time to trim
diff --git a/src/box/lua/merger.c b/src/box/lua/merger.c
index fb860dce580aa3cea4b6352eeb1e3d469d7e3ab5..7efb3f3b64398378232adeca2399de49e0a86a3e 100644
--- a/src/box/lua/merger.c
+++ b/src/box/lua/merger.c
@@ -115,8 +115,8 @@ decode_header(struct ibuf *buf, size_t *len_p)
 static void
 encode_header(struct ibuf *output_buffer, uint32_t result_len)
 {
-	ibuf_reserve(output_buffer, mp_sizeof_array(result_len));
-	output_buffer->wpos = mp_encode_array(output_buffer->wpos, result_len);
+	void *wpos = xibuf_alloc(output_buffer, mp_sizeof_array(result_len));
+	mp_encode_array(wpos, result_len);
 }
 
 /**
@@ -596,10 +596,10 @@ luaL_merge_source_buffer_next(struct merge_source *base,
 		return -1;
 	}
 	--source->remaining_tuple_count;
-	source->buf->rpos = (char *) tuple_end;
 	if (format == NULL)
 		format = tuple_format_runtime;
 	struct tuple *tuple = tuple_new(format, tuple_beg, tuple_end);
+	ibuf_consume_before(source->buf, tuple_end);
 	if (tuple == NULL)
 		return -1;
 
@@ -1140,9 +1140,8 @@ encode_result_buffer(struct lua_State *L, struct merge_source *source,
 	       merge_source_next(source, NULL, &tuple)) == 0 &&
 	       tuple != NULL) {
 		uint32_t bsize = tuple_bsize(tuple);
-		ibuf_reserve(output_buffer, bsize);
-		memcpy(output_buffer->wpos, tuple_data(tuple), bsize);
-		output_buffer->wpos += bsize;
+		void *wpos = xibuf_alloc(output_buffer, bsize);
+		memcpy(wpos, tuple_data(tuple), bsize);
 		result_len_offset += bsize;
 		++result_len;
 
diff --git a/src/box/lua/net_box.c b/src/box/lua/net_box.c
index 714766d920fd7b025fd111eec70820e4ac65154d..e98efd39972835c1be40b8fef0c3fd62aca11db2 100644
--- a/src/box/lua/net_box.c
+++ b/src/box/lua/net_box.c
@@ -254,6 +254,8 @@ struct netbox_transport {
 	struct ibuf send_buf;
 	/** Connection receive buffer. */
 	struct ibuf recv_buf;
+	/** Size of the last received message. */
+	size_t last_msg_size;
 	/** Signalled when send_buf becomes empty. */
 	struct fiber_cond on_send_buf_empty;
 	/** Next request id. */
@@ -506,6 +508,7 @@ netbox_transport_create(struct netbox_transport *transport)
 	iostream_clear(&transport->io);
 	ibuf_create(&transport->send_buf, &cord()->slabc, NETBOX_READAHEAD);
 	ibuf_create(&transport->recv_buf, &cord()->slabc, NETBOX_READAHEAD);
+	transport->last_msg_size = 0;
 	fiber_cond_create(&transport->on_send_buf_empty);
 	transport->next_sync = 1;
 	transport->requests = mh_i64ptr_new();
@@ -563,6 +566,7 @@ netbox_transport_set_error(struct netbox_transport *transport)
 	/* Reset buffers. */
 	ibuf_reinit(&transport->send_buf);
 	ibuf_reinit(&transport->recv_buf);
+	transport->last_msg_size = 0;
 	fiber_cond_broadcast(&transport->on_send_buf_empty);
 	/* Complete requests and clean up the hash. */
 	struct mh_i64ptr_t *h = transport->requests;
@@ -1120,7 +1124,7 @@ netbox_transport_communicate(struct netbox_transport *transport, size_t limit)
 						"Peer closed");
 				return -1;
 			} if (rc > 0) {
-				recv_buf->wpos += rc;
+				VERIFY(ibuf_alloc(recv_buf, rc) != NULL);
 			} else if (rc == IOSTREAM_ERROR) {
 				goto io_error;
 			} else {
@@ -1134,7 +1138,7 @@ netbox_transport_communicate(struct netbox_transport *transport, size_t limit)
 			ssize_t rc = iostream_write(io, send_buf->rpos,
 						    ibuf_used(send_buf));
 			if (rc >= 0) {
-				send_buf->rpos += rc;
+				ibuf_consume(send_buf, rc);
 				if (ibuf_used(send_buf) == 0)
 					fiber_cond_broadcast(on_send_buf_empty);
 			} else if (rc == IOSTREAM_ERROR) {
@@ -1171,6 +1175,7 @@ static int
 netbox_transport_send_and_recv(struct netbox_transport *transport,
 			       struct xrow_header *hdr)
 {
+	ibuf_consume(&transport->recv_buf, transport->last_msg_size);
 	while (true) {
 		size_t required;
 		size_t data_len = ibuf_used(&transport->recv_buf);
@@ -1190,10 +1195,11 @@ netbox_transport_send_and_recv(struct netbox_transport *transport,
 			required = size + len;
 			if (data_len >= required) {
 				const char *body_end = rpos + len;
-				transport->recv_buf.rpos = (char *)body_end;
-				return xrow_header_decode(
-					hdr, &rpos, body_end,
-					/*end_is_exact=*/true);
+				int rc = xrow_header_decode(
+						hdr, &rpos, body_end,
+						/*end_is_exact=*/true);
+				transport->last_msg_size = body_end - bufpos;
+				return rc;
 			}
 		}
 		if (netbox_transport_communicate(transport, required) != 0)
diff --git a/src/box/lua/tuple.lua b/src/box/lua/tuple.lua
index 33aa444849b45d84fc154b8197d40b56fde9e23f..3c952fdfccbd3e10aef71c4dd2f73d211989b5b3 100644
--- a/src/box/lua/tuple.lua
+++ b/src/box/lua/tuple.lua
@@ -270,9 +270,7 @@ end
 local function tuple_to_msgpack(buf, tuple)
     assert(ffi.istype(tuple_t, tuple))
     local bsize = builtin.box_tuple_bsize(tuple)
-    buf:reserve(bsize)
-    builtin.box_tuple_to_buf(tuple, buf.wpos, bsize)
-    buf.wpos = buf.wpos + bsize
+    builtin.box_tuple_to_buf(tuple, buf:alloc(bsize), bsize)
 end
 
 local function tuple_bsize(tuple)
diff --git a/src/httpc.c b/src/httpc.c
index 025346e149bfdf33357c4381d04ab95fdc3c30c4..14880200d1feeb1abd2210802505c7a1801abb97 100644
--- a/src/httpc.c
+++ b/src/httpc.c
@@ -68,7 +68,7 @@ curl_easy_io_read_cb(char *buffer, size_t size, size_t nitems, void *ctx)
 
 	size_t read_len = ibuf_len < buffer_size ? ibuf_len : buffer_size;
 	memcpy(buffer, req->send.rpos, read_len);
-	req->send.rpos += read_len;
+	ibuf_consume(&req->send, read_len);
 
 	fiber_cond_broadcast(&req->io_send_cond);
 	return read_len;
@@ -541,7 +541,7 @@ httpc_request_io_read(struct httpc_request *req, char *buf, size_t len,
 		if (copied == ibuf_len)
 			ibuf_reset(&req->io_recv);
 		else
-			req->io_recv.rpos += copied;
+			ibuf_consume(&req->io_recv, copied);
 	}
 
 	if (copied < len && recv_len > 0) {
diff --git a/src/lib/core/coio_buf.h b/src/lib/core/coio_buf.h
index 0d90a483c06d7d73aa6ee93a123c087651fcf702..110cc700c5b598bf722f3354f7113266bf2602d7 100644
--- a/src/lib/core/coio_buf.h
+++ b/src/lib/core/coio_buf.h
@@ -50,7 +50,7 @@ coio_bread(struct iostream *io, struct ibuf *buf, size_t sz)
 	ssize_t n = coio_read_ahead(io, buf->wpos, sz, ibuf_unused(buf));
 	if (n < 0)
 		diag_raise();
-	buf->wpos += n;
+	VERIFY(ibuf_alloc(buf, n) != NULL);
 	return n;
 }
 
@@ -68,7 +68,7 @@ coio_bread_timeout(struct iostream *io, struct ibuf *buf, size_t sz,
 			                    timeout);
 	if (n < 0)
 		diag_raise();
-	buf->wpos += n;
+	VERIFY(ibuf_alloc(buf, n) != NULL);
 	return n;
 }
 
@@ -80,7 +80,7 @@ coio_breadn(struct iostream *io, struct ibuf *buf, size_t sz)
 	ssize_t n = coio_readn_ahead(io, buf->wpos, sz, ibuf_unused(buf));
 	if (n < 0)
 		diag_raise();
-	buf->wpos += n;
+	VERIFY(ibuf_alloc(buf, n) != NULL);
 	return n;
 }
 
@@ -99,7 +99,7 @@ coio_breadn_timeout(struct iostream *io, struct ibuf *buf, size_t sz,
 			                     timeout);
 	if (n < 0)
 		diag_raise();
-	buf->wpos += n;
+	VERIFY(ibuf_alloc(buf, n) != NULL);
 	return n;
 }
 
diff --git a/src/lua/buffer.lua b/src/lua/buffer.lua
index 9fc5ee8fda2a5a09d9bb9dad0b95bcbdbf5e5b9b..6fa8457829c1d34b75ec9834c0d6177498b346c3 100644
--- a/src/lua/buffer.lua
+++ b/src/lua/buffer.lua
@@ -193,6 +193,13 @@ local function ibuf_read(buf, size)
     return rpos
 end
 
+local function ibuf_consume(buf, size)
+    checkibuf(buf, 'consume')
+    checksize(buf, size)
+    utils.poison_memory_region(buf.rpos, size);
+    buf.rpos = buf.rpos + size
+end
+
 local function ibuf_serialize(buf)
     local properties = { rpos = buf.rpos, wpos = buf.wpos }
     return { ibuf = properties }
@@ -207,6 +214,7 @@ local ibuf_methods = {
 
     checksize = ibuf_checksize;
     read = ibuf_read;
+    consume = ibuf_consume;
     __serialize = ibuf_serialize;
 
     size = ibuf_used;
diff --git a/src/lua/httpc.lua b/src/lua/httpc.lua
index e694f1fc1db4e7d48e2a740fce11ce91258b24b3..a8f058bf6acb41ec0df033d9c96cec42845b90a7 100644
--- a/src/lua/httpc.lua
+++ b/src/lua/httpc.lua
@@ -424,7 +424,7 @@ local function io_read(self, opts, timeout)
     local len = check(self, chunk, delimiter)
     if len ~= nil then
         local data = ffi.string(rbuf.rpos, len)
-        rbuf.rpos = rbuf.rpos + len
+        rbuf:consume(len)
         return data
     end
 
@@ -438,15 +438,15 @@ local function io_read(self, opts, timeout)
             self._errno = nil
             local len = rbuf:size()
             local data = ffi.string(rbuf.rpos, len)
-            rbuf.rpos = rbuf.rpos + len
+            rbuf:consume(len)
             return data
         else
-            rbuf.wpos = rbuf.wpos + res
+            rbuf:alloc(res)
             local len = check(self, chunk, delimiter)
             if len ~= nil then
                 self._errno = nil
                 local data = ffi.string(rbuf.rpos, len)
-                rbuf.rpos = rbuf.rpos + len
+                rbuf:consume(len)
                 return data
             end
         end
diff --git a/src/lua/socket.lua b/src/lua/socket.lua
index 56671728a4732492a4ce36dccdfff6b25256130b..52694de379a761801f376fa4468a0109615a5b20 100644
--- a/src/lua/socket.lua
+++ b/src/lua/socket.lua
@@ -694,7 +694,7 @@ local function read(self, limit, timeout, check, ...)
     if len ~= nil then
         self._errno = nil
         local data = ffi.string(rbuf.rpos, len)
-        rbuf.rpos = rbuf.rpos + len
+        rbuf:consume(len)
         return data
     end
 
@@ -709,15 +709,15 @@ local function read(self, limit, timeout, check, ...)
             self._errno = nil
             local len = rbuf:size()
             local data = ffi.string(rbuf.rpos, len)
-            rbuf.rpos = rbuf.rpos + len
+            rbuf:consume(len)
             return data
         elseif res ~= nil then
-            rbuf.wpos = rbuf.wpos + res
+            rbuf:alloc(res)
             local len = check(self, limit, ...)
             if len ~= nil then
                 self._errno = nil
                 local data = ffi.string(rbuf.rpos, len)
-                rbuf.rpos = rbuf.rpos + len
+                rbuf:consume(len)
                 return data
             end
         elseif not errno_is_transient[self._errno] then