SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e8243ce40187ed743e90726e5fd104006136011976ad2e7b7ded68e18579b5a2' 
  AND token = 'wYlMves50xDehzFqAUKSQ+Ce1RVxsc9rptMXsiIIEiw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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