SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81af31bdd5786ac0f2550885c4677369c8ba6b313782de8d91b583176caae35a' 
  AND token = 'kKsdsreAMZtVOCHZEu8XBJpj9pnziLanaE1hZWaLTFY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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