I had this discussion in my workplace and wanted to share and get opinions from the folks here. (I suspect StackOverflow might not appreciate such open ended questions).
Context: We have a microservice involved in pricing signalling to our users. We have an endpoint which have the following:
- Input: an array of item ID’s
- Output: the expected final price of the given items.
The item prices are quite volatile (and no, it is not crypto related), and is dependent on things like instantaneous supply-demand, promotions, etc.
Since the prices change quite frequently, it became a requirement that we commit to the price that was shown to the user initially, up to a certain time period (eg 5 min after the price was calculated). This improves the UX since the user will be charged as according to what they expected at the start.
Currently, in our system, we achieve this via a JWT, which contains all the details in the request, the obligatory signature, and the expiry set to 5 min from the time it was generated.
After generating this receipt, the FE can then call the endpoint with the JWT which does the actual payment processing using the params encoded in the token. This way, we know that the params + the total cost that is quoted in the JWT originates from our service since we verify that we signed it.
And the system evolves once more. We see that in the system, there is this mechanism, that if the token is expired, we do not reject the request at the charging step. Instead, we call the price endpoint internally using the params provided, and check if the price is the same as in the expired JWT. If it is the same, we process it as normal despite the JWT being expired.
This is where the contention lies. I believe that we should force the user to procure another non-expired JWT and removing this complex logic while others believe in the value of this improved UX where the user doesn’t need to restart the whole flow again.
What do y’all think? Which way would y’all architect the endpoint? Or is there something fundamentally wrong with our design (maybe JWT is not the best suited for this use case)?
Just my opinion here but using a signed JWT instead of a server local variable seems needlessly risky for communicating a price. Considering the potential liability to the company if your signing token is compromised I’d much rather send the prices to the user and keep a server local copy tied to the account/session/auth token. When the user tries to confirm the price we’d just pull the information from local storage.
In terms of your primary question though… I can see the UX advantage of honoring the expired token if prices were stable but I’d probably roll out an MVP without that feature fully developed but with some logging to flag how often it’d activate - throw the statistics at business people and let them ponder how often it’d activate.
That all said, this is an API not a GUI so I really don’t care as much about the UX since the consumer can just automate resubmitting for a new token - especially if we’re putting together an SDK or code samples for clients to run the requests and double especially if we’re controlling both ends with a distributed binary (but that doesn’t sound like the case here).
Actually, we are controlling both ends. But the issue is that frontend have rather limited bandwidth most of the time (sadly the truth is that despite that your own team wants to make things clean, other teams may not have the same stance).