SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3421dc8047ebef2d20ac6372af17ae20f236cb3ac406c4d98db1f70e4d55c19f' 
  AND token = '7TN8ZgJ5i+GK6IVOj/P9d2uDrjGxiZB/+4+rFPJZWMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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