SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8475500b5f59d90dd266553da86843c3c9f3c0e2543b9bc8453ef45b28a994b' 
  AND token = 'k9L8/xHsxfDpHvNxn9bnX+jqMdQs4hE71lnAjcA1Dq8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}