SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef618e70aa4bd665d9673b3492996c95d912963868d69513312a6419206e9a3b' 
  AND token = '3txDPoiNiKMlUcw3WSdRdKMU52MjB7LoaOFTUMrzMxw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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