diff --git a/lib/dry/schema/key_validator.rb b/lib/dry/schema/key_validator.rb
index e9ad86c6..70acf708 100644
--- a/lib/dry/schema/key_validator.rb
+++ b/lib/dry/schema/key_validator.rb
@@ -21,7 +21,7 @@ def call(result)
         input = result.to_h
 
         input_paths = key_paths(input)
-        key_paths = key_map.to_dot_notation
+        key_paths = key_map.to_dot_notation.sort
 
         input_paths.each do |path|
           error_path = validate_path(key_paths, path)
@@ -40,20 +40,31 @@ def call(result)
       def validate_path(key_paths, path)
         if path[INDEX_REGEX]
           key = path.gsub(INDEX_REGEX, BRACKETS)
-
-          if key_paths.none? { paths_match?(key, _1) }
+          if none_key_paths_match?(key_paths, key)
             arr = path.gsub(INDEX_REGEX) { ".#{_1[1]}" }
             arr.split(DOT).map { DIGIT_REGEX.match?(_1) ? Integer(_1, 10) : _1.to_sym }
           end
-        elsif key_paths.none? { paths_match?(path, _1) }
+        elsif none_key_paths_match?(key_paths, path)
           path
         end
       end
 
       # @api private
-      def paths_match?(input_path, key_path)
-        residue = key_path.sub(input_path, "")
-        residue.empty? || residue.start_with?(DOT, BRACKETS)
+      def none_key_paths_match?(key_paths, path)
+        !any_key_paths_match?(key_paths, path)
+      end
+
+      # @api private
+      def any_key_paths_match?(key_paths, path)
+        find_path(key_paths, path, false) ||
+          find_path(key_paths, path + DOT, true) ||
+          find_path(key_paths, path + BRACKETS, true)
+      end
+
+      # @api private
+      def find_path(key_paths, path, prefix_match)
+        key = key_paths.bsearch { |key_path| key_path >= path }
+        prefix_match ? key&.start_with?(path) : key == path
       end
 
       # @api private
diff --git a/spec/integration/schema/key_searching_algorithm_spec.rb b/spec/integration/schema/key_searching_algorithm_spec.rb
new file mode 100644
index 00000000..595cf232
--- /dev/null
+++ b/spec/integration/schema/key_searching_algorithm_spec.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+RSpec.describe Dry::Schema, "key searching algorithm" do
+  it "works properly with keys that are prefixes of other keys" do
+    schema = Dry::Schema.define do
+      config.validate_keys = true
+
+      required(:a).filled(:string)
+      required(:fooA).filled(:string)
+      required(:foo).array(:hash) do
+        required(:bar).filled(:string)
+      end
+    end
+
+    expect(schema.(a: "string", fooA: "string", foo: "string").errors.to_h)
+      .to eql({foo: ["must be an array"]})
+  end
+end