static object parallelLock = new object(); 
        internal void AddUsage(TraceRecord query)
        {
            int i = 0; 
            var MDX_upper = query.MDX.ToUpper(); -- строка 500-8000 символов. 
            if (true)
            {
                Parallel.ForEach(cubeElements, cubeElement =>
                {
                    if (FastIndexOf(MDX_upper, cubeElement.NameUpper) > 0) -- NameUpper строка 10-30 символов 
                    {
                        lock (parallelLock)
                        {
// обработка ....
                        }
                    }
                }
                );
            }
}

static int FastIndexOf(string source, string pattern) {
  if (pattern == null) throw new ArgumentNullException();
  if (pattern.Length == 0) return 0;
  if (pattern.Length == 1) return source.IndexOf(pattern[0]);
 bool found;
  int limit = source.Length - pattern.Length + 1;
  if (limit < 1) return -1;
 // Store the first 2 characters of "pattern"
  char c0 = pattern[0];
  char c1 = pattern[1];
 // Find the first occurrence of the first character
  int first = source.IndexOf(c0, 0, limit);
 while (first != -1) {
   // Check if the following character is the same like
    // the 2nd character of "pattern"
    if (source[first + 1] != c1) {
      first = source.IndexOf(c0, ++first, limit - first);
      continue;
    }
   // Check the rest of "pattern" (starting with the 3rd character)
    found = true;
    for (int j = 2; j < pattern.Length; j++)
      if (source[first + j] != pattern[j]) {
        found = false;
        break;
      }
   // If the whole word was found, return its index, otherwise try again
    if (found) return first;
    first = source.IndexOf(c0, ++first, limit - first);
  }
  return -1;
}

                if (source[first + 1] != c1)
00B59EF3  mov         edx,dword ptr [ebp-54h]  
00B59EF6  inc         edx  
00B59EF7  mov         ecx,dword ptr [ebp-3Ch]  
00B59EFA  cmp         dword ptr [ecx],ecx  
00B59EFC  call        67C33ED0  
00B59F01  mov         dword ptr [ebp-0A0h],eax  
00B59F07  mov         eax,dword ptr [ebp-0A0h]  
00B59F0D  cmp         eax,dword ptr [ebp-50h]  
00B59F10  setne       al  
00B59F13  movzx       eax,al  
00B59F16  mov         dword ptr [ebp-6Ch],eax  
00B59F19  cmp         dword ptr [ebp-6Ch],0  
00B59F1D  je          00B59F4F 

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp4
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] strs = new string[] {
                "AAC00", "1248A", "1258A", "1348A", "D248A", "1D48A", "12D8A", "1248D",
                "A0C", "1048A", "0258A", "0348A", "D208A", "1D08A", "10D8A", "1240D",
                "A7C", "1247A", "1257A", "13487", "D247A", "1D47A", "17D8A", "1278D",
            };

            int MAX = 10000;
            int MAX2 = 1000;
            var texts = Enumerable.Range(1, MAX).Select(
                g => string.Join("", Enumerable.Range(1, MAX2).Select(
                    gg => Guid.NewGuid().ToString().ToUpper()).ToArray())
                ).ToList();

            Int64[] found = new Int64[strs.Length];
            InitFound(strs, found);
            var sw0 = new Stopwatch();
            sw0.Start();
            Parallel.ForEach(texts, text =>
            {
                for (int i = 0; i < strs.Length; i++)
                    if (text.Contains(strs[i]))
                        found[i]++;
            });
            sw0.Stop();
            Debug.WriteLine(string.Join(",", found.Select(x => x).ToArray()));

            InitFound(strs, found);
            var sw1 = new Stopwatch();
            sw1.Start();
            Parallel.ForEach(texts, text =>
            {
                for (int i = 0; i < strs.Length; i++)
                    if (text.Contains(strs[i]))
                        found[i]++;
            });
            sw1.Stop();
            Debug.WriteLine(string.Join(",", found.Select(x => x).ToArray()));


            Console.WriteLine($"time0 = {sw0.ElapsedMilliseconds} time1 = {sw1.ElapsedMilliseconds}");
            Console.ReadKey();
        }

        private static void InitFound(string[] strs, long[] found)
        {
            for (int i = 0; i < strs.Length; i++)
                found[i] = 0;
        }

    }
}