SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c31481ed890bb915e28b27bd6997a767d252e6c252542dc7d6e2f6d5819a97d9' 
  AND token = 'k3GhK/PDiMf+pBU9DhlvcVzpnyze5MLCXrq0FFhRi0U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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