What you can prove

Every exercise here asks one question. The whole course is the difference between reading the answer to it and being able to prove it.

This page is the record of which is which for you. It is worth being exact about what it can and cannot see, because a page that overstated this would be the walkthrough this course exists to avoid.

It can see what you did on this site. The questions you answered, the hints you opened, the solution you read, the notes you wrote, the commands you replayed. All of that has been stored in your own browser all along, by the pages themselves. Nothing was uploaded, there is no account, and until this page existed nothing ever read any of it back.

It cannot see whether you fixed anything. Nothing typed into a page changes a real system, so nothing you do here is proof of anything. Only tse check knows, because only tse check ran the assertions against genuinely broken containers. That is why the box below is here, and it is the only thing that turns a question into a statement.

Where you are

26 exercises.

Paste the output of tse progress --json

This is the only thing that can tell this page you fixed anything. It stays in your browser. There is no account and nothing is uploaded.

Import

Linux and CLI

• Can I prove which resource actually ran out?

  Not started.

  The disk has plenty of space and the writes still fail

• Can I prove which account the process is actually running as?

  Not started.

  The file is right there and the service cannot read it

Docker

• Can I prove the application started at all?

  Not started.

  Service unavailable after a release

• Can I prove the application can reach its database?

  Not started.

  Application loads but customer data does not

• Can I prove why the database refused the connection?

  Not started.

  Same symptom as the last ticket, different cause

Networking, DNS, TLS

• Can I prove what the server is presenting, rather than that it is up?

  Not started.

  The nightly upload stopped and nothing changed

• Can I prove the server is refusing the name rather than the caller?

  Not started.

  The new address fails and the old one works

• Can I prove how far the connection got before it failed?

  Not started.

  Same two addresses, and the certificate is fine

Kubernetes

• Can I prove whether the workload was ever able to start?

  Not started.

  A release went out and the new version never arrived

• Can I prove why a container never started, when it has produced no output?

  Not started.

  The service is down and there are no logs at all

• Can I prove whether the application crashed or was killed?

  Not started.

  The service restarts every few minutes and nobody changed the code

• Can I prove whether the Service is actually routing to any pods?

  Not started.

  Every pod is healthy and the service still answers nothing

• Can I prove why a running pod is being excluded from its Service?

  Not started.

  Same symptom as the last ticket, and the labels are correct

APIs

• Can I prove whether the caller is unknown, unauthenticated, or no longer permitted?

  Not started.

  Integration rejected with an authentication error

• Can I prove this is a permissions failure rather than an authentication failure?

  Not started.

  Export fails for one user but works for another

• Can I prove the route the customer is calling still exists?

  Not started.

  Integration stopped working and nothing on the customer side changed

• Can I prove the failure depends on request rate rather than on the data?

  Not started.

  Batch job succeeds at the start and fails partway through

SQL and PostgreSQL

• Can I prove the report is asking for what the customer thinks it asks for?

  Not started.

  A report is quietly missing customers

• Can I prove which of the two numbers is the wrong one?

  Not started.

  Two reports disagree about the same number

• Can I prove how the database is finding the rows, not just how long it took?

  Not started.

  A report that was instant is now painful

Observability

• Can I prove what this customer is seeing, rather than what everyone is seeing?

  Not started.

  The dashboard is green and one customer is timing out

• Can I prove where the identifier the customer holds stops?

  Not started.

  They keep sending you the reference and you have no record of it

Customer communication

• Can I prove to the customer what happened without them having to trust me?

  Not started.

  The update you owe a customer once the outage is over

• Can I hand this to an engineer without them needing to gather the evidence again?

  Not started.

  The escalation that gets picked up instead of handed back

Mixed incidents

• Can I prove the customer's requests are reaching the application at all?

  Not started.

  Every health check is green and the customer still gets nothing

• Can I prove the request was understood, rather than merely accepted?

  Not started.

  Their sync reports success on every run and nothing ever arrives

If it says nothing is proven

That is the honest answer rather than a fault. Run the exercises in a Codespace or a local clone, then:

tse progress --json

Paste what it prints into the box above. Your terminal and your browser have no other way to reach each other, which is a consequence of this course keeping everything on your own machine rather than an oversight.