SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3de70017b3a397ffa5863e681d4b29e4420be1476a91dd021e2441134b88cf7d' 
  AND token = 'fh5ZTTznvE4GbZVzVVY5dEcWylNr6jaARCCP0p91PFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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