SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c79f0998b3745828fdf0269f71e78a3556575b85a5b9c1c6bbdee407fd760713' 
  AND token = 'JQySk1UgqAKCi4TgGvD/+bbDhz7wfjt63ofmJEyhA68=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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