SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '87a9821c5a4fa3f78cf9876d36114c0c6c792435572fc5d1e4f9b388d44d0444' 
  AND token = 'Y2E+YLwibiCkFjWotm/1KVdrhjzlngsBp5TaWY9pMzA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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