SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8ac73264debdb6011da8925176f3ccc738b68181095242e6598516098f7ad3d' 
  AND token = '6QQmRV4rSfKZsJQkf8d5TqlF6rEQuR3+Brmu+sSMBus=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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