Know these precisely, and be comfortably honest about everything else. That combination earns more trust than pretending to know it all.
Term | Plain English | Why you care |
|---|---|---|
Endpoint | A specific address you can call | The basic unit of an API's surface area |
Payload | The actual data sent in a request or response | What you're actually reading when you review a spec |
Latency | How long a call takes to get a response | Directly affects whether your API feels "instant" or "slow" to a developer |
Throughput | How many requests the system can handle per second | Determines whether you can support your biggest customer at their peak |
Idempotency | Calling the same request twice has the same effect as once | Prevents duplicate charges, duplicate orders, duplicate everything |
Webhook | The server pushes an event to you, instead of you polling for it | Real-time behavior without constant checking |
Rate limit | A cap on how many calls a caller can make in a time window | Protects your infrastructure and your other customers |
SDK | Pre-built code in a specific language that wraps your API, so a developer doesn't call raw HTTP | Lowers the bar to integrate; a real DX investment, not a nice-to-have |
Breaking change | Any change that could cause an existing, correctly-written integration to fail | The line that separates a routine deploy from an incident |
Deprecation | An announced, time-bound plan to eventually remove something | The respectful way to make a breaking change |
SLA | Service Level Agreement — a formal promise about uptime or performance, often with financial penalties attached | A business commitment, not just a technical target |
Schema | The formal, structured definition of what a request or response must look like | The enforceable version of "the contract" from Lesson 1.1 |
Sandbox | A safe, fake-data environment for testing integrations | A core DX requirement — nobody wants to test against production |
Changelog | A dated, public record of every change to the API | The single artifact that determines whether developers trust you enough to auto-update |
Backward compatibility | Old code keeps working after you ship something new | The whole point of Lesson 3.2, in three words |
THREE SENTENCES WORTH MORE THAN ANY AMOUNT OF JARGON FLUENCY
"Is this a breaking change for anyone currently integrated?"
"What does the error case look like, not just the success case?"
"I don't follow that part — can you explain it as if I were an outside developer?"
YOUR MOVE THIS WEEK
In your next engineering conversation about an API, use three of these ter