SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '812755fed9e941360f9a53c60a91fedceb8fd4e3f30067129105128ee1dac773' 
  AND token = '6Za4hCF1MHKfRKsiCY7J1IGIGyLCULd+HqPLbsEFgZk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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