diff --git a/include/engine/polyline_compressor.hpp b/include/engine/polyline_compressor.hpp
index b2a505764..af58b0422 100644
--- a/include/engine/polyline_compressor.hpp
+++ b/include/engine/polyline_compressor.hpp
@@ -12,7 +12,7 @@ namespace osrm::engine
 {
 namespace detail
 {
-std::string encode(std::vector<int> &numbers);
+void encode(int number_to_encode, std::string &output);
 std::int32_t decode_polyline_integer(std::string::const_iterator &first,
                                      std::string::const_iterator last);
 } // namespace detail
@@ -30,27 +30,24 @@ std::string encodePolyline(CoordVectorForwardIter begin, CoordVectorForwardIter
         return {};
     }
 
-    std::vector<int> delta_numbers;
-    BOOST_ASSERT(size > 0);
-    delta_numbers.reserve((size - 1) * 2);
+    std::string output;
+    // just a guess that we will need ~4 bytes per coordinate to avoid reallocations
+    output.reserve(size * 4);
+
     int current_lat = 0;
     int current_lon = 0;
-    std::for_each(
-        begin,
-        end,
-        [&delta_numbers, &current_lat, &current_lon, coordinate_to_polyline](
-            const util::Coordinate loc)
-        {
-            const int lat_diff =
-                std::round(static_cast<int>(loc.lat) * coordinate_to_polyline) - current_lat;
-            const int lon_diff =
-                std::round(static_cast<int>(loc.lon) * coordinate_to_polyline) - current_lon;
-            delta_numbers.emplace_back(lat_diff);
-            delta_numbers.emplace_back(lon_diff);
-            current_lat += lat_diff;
-            current_lon += lon_diff;
-        });
-    return detail::encode(delta_numbers);
+    for (auto it = begin; it != end; ++it)
+    {
+        const int lat_diff =
+            std::round(static_cast<int>(it->lat) * coordinate_to_polyline) - current_lat;
+        const int lon_diff =
+            std::round(static_cast<int>(it->lon) * coordinate_to_polyline) - current_lon;
+        detail::encode(lat_diff, output);
+        detail::encode(lon_diff, output);
+        current_lat += lat_diff;
+        current_lon += lon_diff;
+    }
+    return output;
 }
 
 // Decodes geometry from polyline format
diff --git a/src/engine/polyline_compressor.cpp b/src/engine/polyline_compressor.cpp
index 3d4500643..7435fed3f 100644
--- a/src/engine/polyline_compressor.cpp
+++ b/src/engine/polyline_compressor.cpp
@@ -10,9 +10,19 @@
 namespace osrm::engine::detail // anonymous to keep TU local
 {
 
-std::string encode(int number_to_encode)
+void encode(int number_to_encode, std::string &output)
 {
-    std::string output;
+    if (number_to_encode < 0)
+    {
+        const unsigned binary = std::llabs(number_to_encode);
+        const unsigned twos = (~binary) + 1u;
+        const unsigned shl = twos << 1u;
+        number_to_encode = static_cast<int>(~shl);
+    }
+    else
+    {
+        number_to_encode <<= 1u;
+    }
     while (number_to_encode >= 0x20)
     {
         const int next_value = (0x20 | (number_to_encode & 0x1f)) + 63;
@@ -22,31 +32,6 @@ std::string encode(int number_to_encode)
 
     number_to_encode += 63;
     output += static_cast<char>(number_to_encode);
-    return output;
-}
-
-std::string encode(std::vector<int> &numbers)
-{
-    std::string output;
-    for (auto &number : numbers)
-    {
-        if (number < 0)
-        {
-            const unsigned binary = std::llabs(number);
-            const unsigned twos = (~binary) + 1u;
-            const unsigned shl = twos << 1u;
-            number = static_cast<int>(~shl);
-        }
-        else
-        {
-            number <<= 1u;
-        }
-    }
-    for (const int number : numbers)
-    {
-        output += encode(number);
-    }
-    return output;
 }
 
 // https://developers.google.com/maps/documentation/utilities/polylinealgorithm