diff --git a/codeflash/api/aiservice.py b/codeflash/api/aiservice.py
index f337a985..00585f9c 100644
--- a/codeflash/api/aiservice.py
+++ b/codeflash/api/aiservice.py
@@ -353,6 +353,59 @@ def get_new_explanation(  # noqa: D417
         console.rule()
         return ""
 
+    def generate_ranking(  # noqa: D417
+        self, trace_id: str, diffs: list[str], optimization_ids: list[str], speedups: list[float]
+    ) -> list[int] | None:
+        """Optimize the given python code for performance by making a request to the Django endpoint.
+
+        Parameters
+        ----------
+        - source_code (str): The python code to optimize.
+        - optimized_code (str): The python code generated by the AI service.
+        - dependency_code (str): The dependency code used as read-only context for the optimization
+        - original_line_profiler_results: str - line profiler results for the baseline code
+        - optimized_line_profiler_results: str - line profiler results for the optimized code
+        - original_code_runtime: str - runtime for the baseline code
+        - optimized_code_runtime: str - runtime for the optimized code
+        - speedup: str - speedup of the optimized code
+        - annotated_tests: str - test functions annotated with runtime
+        - optimization_id: str - unique id of opt candidate
+        - original_explanation: str - original_explanation generated for the opt candidate
+
+        Returns
+        -------
+        - List[OptimizationCandidate]: A list of Optimization Candidates.
+
+        """
+        payload = {
+            "trace_id": trace_id,
+            "diffs": diffs,
+            "speedups": speedups,
+            "optimization_ids": optimization_ids,
+            "python_version": platform.python_version(),
+        }
+        logger.info("Generating ranking")
+        console.rule()
+        try:
+            response = self.make_ai_service_request("/rank", payload=payload, timeout=60)
+        except requests.exceptions.RequestException as e:
+            logger.exception(f"Error generating ranking: {e}")
+            ph("cli-optimize-error-caught", {"error": str(e)})
+            return None
+
+        if response.status_code == 200:
+            ranking: list[int] = response.json()["ranking"]
+            console.rule()
+            return ranking
+        try:
+            error = response.json()["error"]
+        except Exception:
+            error = response.text
+        logger.error(f"Error generating ranking: {response.status_code} - {error}")
+        ph("cli-optimize-error-response", {"response_status_code": response.status_code, "error": error})
+        console.rule()
+        return None
+
     def log_results(  # noqa: D417
         self,
         function_trace_id: str,
diff --git a/codeflash/code_utils/code_utils.py b/codeflash/code_utils/code_utils.py
index dfd79a76..4ff01004 100644
--- a/codeflash/code_utils/code_utils.py
+++ b/codeflash/code_utils/code_utils.py
@@ -20,6 +20,23 @@
 ImportErrorPattern = re.compile(r"ModuleNotFoundError.*$", re.MULTILINE)
 
 
+def unified_diff_strings(code1: str, code2: str, fromfile: str = "original", tofile: str = "modified") -> str:
+    """Return the unified diff between two code strings as a single string.
+
+    :param code1: First code string (original).
+    :param code2: Second code string (modified).
+    :param fromfile: Label for the first code string.
+    :param tofile: Label for the second code string.
+    :return: Unified diff as a string.
+    """
+    code1_lines = code1.splitlines(keepends=True)
+    code2_lines = code2.splitlines(keepends=True)
+
+    diff = difflib.unified_diff(code1_lines, code2_lines, fromfile=fromfile, tofile=tofile, lineterm="")
+
+    return "".join(diff)
+
+
 def diff_length(a: str, b: str) -> int:
     """Compute the length (in characters) of the unified diff between two strings.
 
diff --git a/codeflash/optimization/function_optimizer.py b/codeflash/optimization/function_optimizer.py
index c523dcbc..4e624bbc 100644
--- a/codeflash/optimization/function_optimizer.py
+++ b/codeflash/optimization/function_optimizer.py
@@ -39,6 +39,7 @@
     has_any_async_functions,
     module_name_from_file_path,
     restore_conftest,
+    unified_diff_strings,
 )
 from codeflash.code_utils.config_consts import (
     INDIVIDUAL_TESTCASE_TIMEOUT,
@@ -170,9 +171,10 @@ def _process_refinement_results(self) -> OptimizedCandidate | None:
             self.candidate_queue.put(candidate)
 
         self.candidate_len += len(refinement_response)
-        logger.info(
-            f"Added {len(refinement_response)} candidates from refinement, total candidates now: {self.candidate_len}"
-        )
+        if len(refinement_response) > 0:
+            logger.info(
+                f"Added {len(refinement_response)} candidates from refinement, total candidates now: {self.candidate_len}"
+            )
         self.refinement_done = True
 
         return self.get_next_candidate()
@@ -659,6 +661,9 @@ def determine_best_candidate(
         # reassign the shorter code here
         valid_candidates_with_shorter_code = []
         diff_lens_list = []  # character level diff
+        speedups_list = []
+        optimization_ids = []
+        diff_strs = []
         runtimes_list = []
         for valid_opt in valid_optimizations:
             valid_opt_normalized_code = ast.unparse(ast.parse(valid_opt.candidate.source_code.flat.strip()))
@@ -682,12 +687,35 @@ def determine_best_candidate(
             diff_lens_list.append(
                 diff_length(new_best_opt.candidate.source_code.flat, code_context.read_writable_code.flat)
             )  # char level diff
+            diff_strs.append(
+                unified_diff_strings(code_context.read_writable_code.flat, new_best_opt.candidate.source_code.flat)
+            )
+            speedups_list.append(
+                1
+                + performance_gain(
+                    original_runtime_ns=original_code_baseline.runtime, optimized_runtime_ns=new_best_opt.runtime
+                )
+            )
+            optimization_ids.append(new_best_opt.candidate.optimization_id)
             runtimes_list.append(new_best_opt.runtime)
-        diff_lens_ranking = create_rank_dictionary_compact(diff_lens_list)
-        runtimes_ranking = create_rank_dictionary_compact(runtimes_list)
-        # TODO: better way to resolve conflicts with same min ranking
-        overall_ranking = {key: diff_lens_ranking[key] + runtimes_ranking[key] for key in diff_lens_ranking.keys()}  # noqa: SIM118
-        min_key = min(overall_ranking, key=overall_ranking.get)
+        future_ranking = self.executor.submit(
+            ai_service_client.generate_ranking,
+            diffs=diff_strs,
+            optimization_ids=optimization_ids,
+            speedups=speedups_list,
+            trace_id=self.function_trace_id[:-4] + exp_type if self.experiment_id else self.function_trace_id,
+        )
+        concurrent.futures.wait([future_ranking])
+        ranking = future_ranking.result()
+        if ranking:
+            ranking = [x - 1 for x in ranking]
+            min_key = ranking[0]
+        else:
+            diff_lens_ranking = create_rank_dictionary_compact(diff_lens_list)
+            runtimes_ranking = create_rank_dictionary_compact(runtimes_list)
+            # TODO: better way to resolve conflicts with same min ranking
+            overall_ranking = {key: diff_lens_ranking[key] + runtimes_ranking[key] for key in diff_lens_ranking.keys()}  # noqa: SIM118
+            min_key = min(overall_ranking, key=overall_ranking.get)
         best_optimization = valid_candidates_with_shorter_code[min_key]
         # reassign code string which is the shortest
         ai_service_client.log_results(