SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b38dc9db2ebea8c861cfa4b761fcf0b3f3f0ef2e12f8e93b049405fff0eca4d' 
  AND token = 'yHwRXkPNhuWNmLsRmM/XJPw9QEN4ZBVykdxQXVK6tRs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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