diff --git a/benchmark.log b/benchmark.log
new file mode 100644
index 000000000..a776e2970
--- /dev/null
+++ b/benchmark.log
@@ -0,0 +1,14 @@
+Benchmarked in Buk main repository having ~25K ruby files.
+
+                      user     system      total        real
+old-glob          1.019865   0.292442   1.312307 (  1.312549)
+new-index         0.000049   0.000007   0.000056 (  0.000056)
+
+Beign N = number of files
+Beign K = number of files matching the subject/test
+And should be very low (Almost constant)
+
+Space Complexity O(N)
+Time complexity is O(K)
+
+The feature become almost instant 
diff --git a/lib/ruby_indexer/lib/ruby_indexer/file_index.rb b/lib/ruby_indexer/lib/ruby_indexer/file_index.rb
new file mode 100644
index 000000000..06cc306de
--- /dev/null
+++ b/lib/ruby_indexer/lib/ruby_indexer/file_index.rb
@@ -0,0 +1,89 @@
+# typed: false
+# frozen_string_literal: true
+
+# Index:
+# {
+#   "c": ["a/b/c.rb", "a/b/c_test.rb", "a/b/c_integration_test.rb", "a/b/test_c.rb", "a/b/sepc_c.rb", "a/b/integration_test_c.rb"]
+# }
+
+# API:
+# index.search("c") -> ["a/b/c.rb", "a/b/c_test.rb", "a/b/c_integration_test.rb", "a/b/test_c.rb", "a/b/sepc_c.rb", "a/b/integration_test_c.rb"]
+# index.insert("a/b/d.rb")
+# index.insert("a/b/d_test.rb")
+# index.search("d") -> ["a/b/d.rb", "a/b/d_test.rb"]
+# index.delete("a/b/d.rb")
+# index.search("d") -> ["a/b/d_test.rb"]
+# index.delete("a/b/d_test.rb")
+# index.search("d") -> []
+
+module RubyIndexer
+  # The FileIndex class maintains an in-memory index of files for fast lookup.
+  # It allows searching for files based on their base name, handling various test file patterns.
+  class FileIndex # TODO: Provide better naming for just subject/test file index.
+    TEST_REGEX = /^(test_|spec_|integration_test_)|((_test|_spec|_integration_test)$)/
+    def initialize
+      @index = {}
+    end
+
+    # Extract the base name from a file path, removing test prefixes and suffixes
+    def extract_base_name(path)
+      basename = File.basename(path, ".*")
+
+      # Handle patterns like test_hello, spec_hello, integration_test_hello
+      basename = basename.sub(/^(test_|spec_|integration_test_)/, "")
+
+      # Handle patterns like hello_test, hello_spec, hello_integration_test
+      basename = basename.sub(/((_test|_spec|_integration_test)$)/, "")
+
+      basename
+    end
+
+    # Insert a file path into the index
+    def insert(path)
+      base_name = extract_base_name(path)
+      @index[base_name] ||= []
+      @index[base_name] << path
+    end
+
+    # Delete a file path from the index
+    def delete(path)
+      base_name = extract_base_name(path)
+      if @index.key?(base_name)
+        @index[base_name].delete(path)
+        @index.delete(base_name) if @index[base_name].empty?
+      end
+    end
+
+    # Search for files that match the given base name
+    def search(base_name)
+      @index[base_name] || []
+    end
+
+    # Search for files that can be tests of the given base_name
+    def search_test(base_name)
+      return [] if @index[base_name].nil?
+
+      search(base_name).select do |file|
+        File.basename(file, ".*").match?(TEST_REGEX)
+      end
+    end
+
+    def search_subject(base_name)
+      return [] if @index[base_name].nil?
+
+      search(base_name).reject do |file|
+        File.basename(file, ".*").match?(TEST_REGEX)
+      end
+    end
+
+    # Bulk load multiple file paths into the index
+    def bulk_load(paths)
+      paths.each { |path| insert(path) }
+    end
+
+    # Clear the entire index
+    def clear
+      @index.clear
+    end
+  end
+end
diff --git a/lib/ruby_indexer/lib/ruby_indexer/index.rb b/lib/ruby_indexer/lib/ruby_indexer/index.rb
index ec4ecc45b..916929f62 100644
--- a/lib/ruby_indexer/lib/ruby_indexer/index.rb
+++ b/lib/ruby_indexer/lib/ruby_indexer/index.rb
@@ -1,6 +1,8 @@
 # typed: strict
 # frozen_string_literal: true
 
+require_relative "file_index"
+
 module RubyIndexer
   class Index
     class UnresolvableAliasError < StandardError; end
@@ -13,6 +15,9 @@ class IndexNotEmptyError < StandardError; end
     #: Configuration
     attr_reader :configuration
 
+    #: RubyIndexer::FileIndex
+    attr_reader :file_index
+
     #: bool
     attr_reader :initial_indexing_completed
 
@@ -80,6 +85,9 @@ def initialize
       @configuration = RubyIndexer::Configuration.new #: Configuration
 
       @initial_indexing_completed = false #: bool
+
+      # File index for tracking files and their relationships
+      @file_index = FileIndex.new #: FileIndex
     end
 
     # Register an included `hook` that will be executed when `module_name` is included into any namespace
@@ -93,6 +101,7 @@ def delete(uri, skip_require_paths_tree: false)
       key = uri.to_s
       # For each constant discovered in `path`, delete the associated entry from the index. If there are no entries
       # left, delete the constant from the index.
+      # TODO: Adjust file index on delete.
       @uris_to_entries[key]&.each do |entry|
         name = entry.name
         entries = @entries[name]
@@ -348,6 +357,9 @@ def index_all(uris: @configuration.indexable_uris, &block)
           "The index is not empty. To prevent invalid entries, `index_all` can only be called once."
       end
 
+      # Clear the file index at the start of a full indexing
+      @file_index.clear
+
       RBSIndexer.new(self).index_ruby_core
       # Calculate how many paths are worth 1% of progress
       progress_step = (uris.length / 100.0).ceil
@@ -361,6 +373,9 @@ def index_all(uris: @configuration.indexable_uris, &block)
         index_file(uri, collect_comments: false)
       end
 
+      # Bulk load all file paths into the file index
+      @file_index.bulk_load(Dir.glob("**/*.rb"))
+
       @initial_indexing_completed = true
     end
 
@@ -377,6 +392,8 @@ def index_single(uri, source, collect_comments: true)
 
       indexing_errors = listener.indexing_errors.uniq
       indexing_errors.each { |error| $stderr.puts(error) } if indexing_errors.any?
+
+      # TODO: Add file to file index
     rescue SystemStackError => e
       if e.backtrace&.first&.include?("prism")
         $stderr.puts "Prism error indexing #{uri}: #{e.message}"
diff --git a/lib/ruby_lsp/internal.rb b/lib/ruby_lsp/internal.rb
index 420ca665e..c98e813a6 100644
--- a/lib/ruby_lsp/internal.rb
+++ b/lib/ruby_lsp/internal.rb
@@ -86,6 +86,7 @@
 require "ruby_lsp/requests/folding_ranges"
 require "ruby_lsp/requests/formatting"
 require "ruby_lsp/requests/go_to_relevant_file"
+require "ruby_lsp/requests/go_to_relevant_file_v2"
 require "ruby_lsp/requests/hover"
 require "ruby_lsp/requests/inlay_hints"
 require "ruby_lsp/requests/on_type_formatting"
diff --git a/lib/ruby_lsp/requests/go_to_relevant_file_v2.rb b/lib/ruby_lsp/requests/go_to_relevant_file_v2.rb
new file mode 100644
index 000000000..7bba497ec
--- /dev/null
+++ b/lib/ruby_lsp/requests/go_to_relevant_file_v2.rb
@@ -0,0 +1,115 @@
+# typed: strict
+# frozen_string_literal: true
+
+module RubyLsp
+  module Requests
+    # GoTo Relevant File is a custom [LSP
+    # request](https://microsoft.github.io/language-server-protocol/specification#requestMessage)
+    # that navigates to the relevant file for the current document.
+    # Currently, it supports source code file <> test file navigation.
+    class GoToRelevantFileV2 < Request
+      TEST_KEYWORDS = ["test", "spec", "integration_test"]
+
+      TEST_PREFIX_PATTERN = /^(#{TEST_KEYWORDS.join("_|")}_)/
+      TEST_SUFFIX_PATTERN = /(_#{TEST_KEYWORDS.join("|_")})$/
+      TEST_PATTERN = /#{TEST_PREFIX_PATTERN}|#{TEST_SUFFIX_PATTERN}/
+
+      TEST_PREFIX_GLOB = "#{TEST_KEYWORDS.join("_,")}_" #: String
+      TEST_SUFFIX_GLOB = "_#{TEST_KEYWORDS.join(",_")}" #: String
+
+      TEST_REGEX = /^(test_|spec_|integration_test_)|((_test|_spec|_integration_test)$)/
+
+      #: (String path, String workspace_path, RubyIndexer::FileIndex file_index) -> void
+      def initialize(path, workspace_path, file_index)
+        super()
+
+        @file_index = file_index
+        @workspace_path = workspace_path
+        @path = path.delete_prefix(workspace_path) #: String
+      end
+
+      # @override
+      #: -> Array[String]
+      def perform
+        find_relevant_paths
+      end
+
+      private
+
+      #: -> Array[String]
+      def find_relevant_paths
+        # Extract the base name from the current file (without the extension)
+        input_basename = File.basename(@path, File.extname(@path))
+
+        base_name = if input_basename.match?(TEST_PATTERN)
+          # If it's a test file, remove the test prefix/suffix
+          input_basename.gsub(TEST_PATTERN, "")
+        else
+          # If it's a source file, use its base name
+          input_basename
+        end
+
+        # Use the FileIndex to find relevant files via the index
+        candidate_paths = if input_basename.match?(TEST_REGEX)
+          @file_index.search_subject(base_name)
+        else
+          @file_index.search_test(base_name)
+        end
+
+        return [] if candidate_paths.empty?
+
+        # Filter out the current file from the candidates
+        full_path = File.join(@workspace_path, @path)
+        candidates = candidate_paths.reject do |path|
+          path == full_path
+        end
+
+        # Filter to include only files with matching extensions
+        extension = File.extname(@path)
+        candidates = candidates.select do |path|
+          File.extname(path) == extension
+        end
+
+        candidates = candidates.map { |path| File.join(@workspace_path, path) }
+
+        return [] if candidates.empty?
+
+        # Find the most similar paths using Jaccard similarity
+        find_most_similar_with_jaccard(candidates)
+      end
+
+      # Using the Jaccard algorithm to determine the similarity between the
+      # input path and the candidate relevant file paths.
+      # Ref: https://en.wikipedia.org/wiki/Jaccard_index
+      # The main idea of this algorithm is to take the size of interaction and divide
+      # it by the size of union between two sets (in our case the elements in each set
+      # would be the parts of the path separated by path divider.)
+      #: (Array[String] candidates) -> Array[String]
+      def find_most_similar_with_jaccard(candidates)
+        dirs = get_dir_parts(@path)
+
+        _, results = candidates
+          .group_by do |other_path|
+            # For consistency with the current path, convert absolute paths to relative if needed
+            relative_path = if other_path.start_with?(@workspace_path)
+              other_path.delete_prefix(@workspace_path)
+            else
+              other_path
+            end
+
+            other_dirs = get_dir_parts(relative_path)
+            # Similarity score between the two directories
+            (dirs & other_dirs).size.to_f / (dirs | other_dirs).size
+          end
+          .max_by(&:first)
+
+        results || []
+      end
+
+      #: (String path) -> Set[String]
+      def get_dir_parts(path)
+        Set.new(File.dirname(path).split(File::SEPARATOR))
+      end
+    end
+  end
+end
diff --git a/lib/ruby_lsp/server.rb b/lib/ruby_lsp/server.rb
index 14f178d13..431060edf 100644
--- a/lib/ruby_lsp/server.rb
+++ b/lib/ruby_lsp/server.rb
@@ -1,6 +1,8 @@
 # typed: strict
 # frozen_string_literal: true
 
+require "benchmark"
+
 module RubyLsp
   class Server < BaseServer
     # Only for testing
@@ -1181,8 +1183,28 @@ def experimental_go_to_relevant_file(message)
         return
       end
 
+      $stdout = File.new("benchmark.log", "w")
+      $stdout.sync = true
+
+      Benchmark.bm(15) do |x|
+        x.report("old-glob") do
+          Requests::GoToRelevantFile.new(path, @global_state.workspace_path).perform
+        end
+        x.report("new-index") do
+          Requests::GoToRelevantFileV2.new(
+            path,
+            @global_state.workspace_path,
+            @global_state.index.file_index,
+          ).perform
+        end
+      end
+
       response = {
-        locations: Requests::GoToRelevantFile.new(path, @global_state.workspace_path).perform,
+        locations: Requests::GoToRelevantFileV2.new(
+          path,
+          @global_state.workspace_path,
+          @global_state.index.file_index,
+        ).perform,
       }
       send_message(Result.new(id: message[:id], response: response))
     end
diff --git a/test/requests/go_to_relevant_file_test.rb b/test/requests/go_to_relevant_file_test.rb
index a8c93f86d..c93a598e3 100644
--- a/test/requests/go_to_relevant_file_test.rb
+++ b/test/requests/go_to_relevant_file_test.rb
@@ -10,7 +10,11 @@ def test_when_input_is_test_file_returns_array_of_implementation_file_locations
     test_file_path = "/workspace/test/requests/go_to_relevant_file_test.rb"
     expected = ["/workspace/lib/ruby_lsp/requests/go_to_relevant_file.rb"]
 
-    result = RubyLsp::Requests::GoToRelevantFile.new(test_file_path, "/workspace").perform
+    file_index = RubyIndexer::FileIndex.new
+    file_index.insert("/workspace/lib/ruby_lsp/requests/go_to_relevant_file.rb")
+    file_index.insert("/workspace/test/requests/go_to_relevant_file_test.rb")
+
+    result = RubyLsp::Requests::GoToRelevantFile.new(test_file_path, "/workspace", file_index).perform
     assert_equal(expected, result)
   end
 
@@ -22,7 +26,11 @@ def test_when_input_is_implementation_file_returns_array_of_test_file_locations
     impl_path = "/workspace/lib/ruby_lsp/requests/go_to_relevant_file.rb"
     expected = ["/workspace/test/requests/go_to_relevant_file_test.rb"]
 
-    result = RubyLsp::Requests::GoToRelevantFile.new(impl_path, "/workspace").perform
+    file_index = RubyIndexer::FileIndex.new
+    file_index.insert("/workspace/lib/ruby_lsp/requests/go_to_relevant_file.rb")
+    file_index.insert("/workspace/test/requests/go_to_relevant_file_test.rb")
+
+    result = RubyLsp::Requests::GoToRelevantFile.new(impl_path, "/workspace", file_index).perform
     assert_equal(expected, result)
   end