SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7bbaff28daa83ec51ff7ee275b2dc58d7cb8d9caec57c22ea7ebc2996335b45f' 
  AND token = 'OclXEhunGZMmkOe53vGLqbMlt6CZ+BraGKGfMeC9X+A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}