SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f27429b5584617cf14a7fe73e1621ec53846bd5f2b1d824538ff14dfa7efa50a' 
  AND token = 'L5QiDAcVFg2FBaYYsQOYtZy7jzUxxGCBmvz2ZQIESIE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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