Go Gotchas
This happens when you write to a nil map in Go.
What is a panic?
This pattern involves one service calling another, which calls another, creating a long chain.
What is cascading failure (or service chaining)?
CVV stands for this.
What is Card Verification Value?
This status code means "Everything is OK".
What is 200?
This Big O notation represents constant time complexity.
What is O(1)?
The zero value of an interface in Go is this.
What is nil?
This pattern prevents cascading failures by stopping requests to an unhealthy service temporarily.
What is circuit breaker?
This fee is charged every time a card transaction occurs, regardless of amount.
What is a flat fee (or transaction fee)?
You get this code when you successfully create a resource via POST.
What is 201 (Created)?
This sorting algorithm has the best average case of O(n log n) but worst case of O(n²).
What is Quicksort?
This keyword makes a goroutine-safe variable for simple operations like incrementing counters.
What is atomic (or sync/atomic)?
This pattern uses unique IDs to track requests across multiple services.
What is distributed tracing (or correlation ID)?
PCI DSS allows storing card numbers but never this 3-4 digit code.
What is CVV/CVC (or security code)?
This status means "I'm a teapot" - an actual April Fools' joke in the spec.
What is 418?
This data structure uses LIFO while its cousin uses FIFO.
What is a stack (vs. queue)?
Passing this to a goroutine inside a for loop is a classic Go bug.
What is the loop variable (or iterator variable)?
This theorem states you can only guarantee two of: Consistency, Availability, and Partition Tolerance.
What is CAP theorem?
Level II/III card data includes this information for commercial cards to get better rates.
What is line item detail (or tax and PO number)?
This status indicates the client sent too many requests in a given time window.
What is 429 (Too Many Requests)?
This problem asks whether every problem whose solution can be quickly verified can also be quickly solved.
What is P vs NP?
This directive prevents the compiler from moving or optimizing away a variable, often seen as //go:___.
What is noescape (or nosplit/noinline)?
This percentage of uptime equals exactly 4.38 minutes of downtime per month.
What is 99.99% (four nines)?
In payment routing, this is the difference between "dual message" and "single message" systems.
What is authorization + settlement vs. combined (or credit vs. debit processing)?
This status code means the server understood the request but refuses to authorize it - different from 401.
What is 403 (Forbidden)?
This distributed systems problem involves generals trying to coordinate an attack with unreliable messengers.
What is the Byzantine Generals Problem (or Byzantine Fault Tolerance)?