Get an invite
The bars

What good looks like, at every level.

Every interview is read against twelve Competencies. Each has a written bar for Junior, Mid, Senior and Staff, and each level keeps what's below it and adds a line. Your Report reads you against the level you chose, and quotes your words for every line.

  • +Adds to the level below
  • If askedJudged only when the interviewer asks about it
  • Not judged at that level
01

Scoping

Pins down what is being built, for whom, and what is out, before designing.

  1. JuniorBefore drawing, says one thing the system must do, and one assumption about who uses it or how much.
  2. Mid+ Names something that is out, and sizes the reads and the writes separately.
  3. Senior+ Sets a target (a latency, an availability) and names the part of the design it constrains.
  4. Staff+ Names the requirement that would change the architecture, and what would change.
02

Estimation

Turns the Givens into figures (throughput, storage, bandwidth) and uses them.

  1. JuniorTurns one given number into a new figure, out loud, and uses a number to justify one choice.
  2. Mid+ Says the unit, and uses a figure they worked out to size a named component.
  3. Senior+ Sizes both sides: a figure for the writes and a figure for the reads.
  4. Staff+ Names the figure that limits the design, and says why.
03

Solution design

Lays out components and flows that satisfy the requirements end to end.

  1. JuniorConnects a client, a service and a store, and walks one use case through them.
  2. Mid+ Walks two use cases end to end, and says what each component is for.
  3. Senior+ Gives every use case in the brief a path.
  4. Staff+ Names the part that changes first as the system grows, and what it becomes.
04

Data and interfaces

Chooses data models, stores and APIs that fit the access patterns.

  1. JuniorSays what is stored and in what kind of store, and one field kept beside the content.
  2. Mid+ Says why the store fits what it holds, and names one API call with its inputs and output.
  3. Senior+ Chooses the store by how it is looked up.
  4. Staff+ Says how the schema or an API changes without breaking clients.
05

Scalability

Keeps the design working as load grows, separating paths that scale differently.

  1. JuniorTreats reads and writes as separate paths, and says which one is busier.If asked
  2. Mid+ Says how the busier path scales out.
  3. Senior+ Puts a cache or a CDN on the busy path and says what it holds, or shows none is needed.
  4. Staff+ Names what fails first at ten times the load, and the fix.
06

Reliability

Anticipates failures and says what the system does when a part fails.

  1. JuniorSays what happens when a named part fails, and one way the system recovers.If asked
  2. Mid+ Says what happens to the work in flight, and a concrete limit on the recovery.
  3. Senior+ Handles a second failure, in a different part of the design.
  4. Staff+ Says how a failure is kept from spreading, and what keeps working meanwhile.
07

Consistency and async

Handles work that finishes later and the consistency that follows from it.

  1. JuniorNot judged at Junior.
  2. MidSays which work happens later and what starts it, and what the user is told, and when.
  3. Senior+ Says how the client learns the work finished, or how stale a value may be.
  4. Staff+ Says what happens when that work fails or runs twice.
08

Trade-offs

Names alternatives, chooses between them with reasons, and owns the cost.

  1. JuniorNames an alternative to one choice, and a reason tied to the problem.
  2. Mid+ Gives a reason specific to this system, and names what their own pick costs.
  3. Senior+ Says when their choice would stop being right, and what they would change then.
  4. Staff+ Names the decision that is hardest to reverse, and why.
09

Technical depth

Explains how a chosen mechanism actually works, beyond naming it.

  1. JuniorExplains what one technology does in the design, and why it fits.
  2. Mid+ Explains how one mechanism works inside, and one of its limits.
  3. Senior+ Does the same for a second mechanism, elsewhere in the design.
  4. Staff+ Shows how one of those limits shaped a choice.
10

Operability

Makes the system observable, deployable and runnable in production.

  1. JuniorNot judged at Junior.
  2. MidNames a metric for the main path, and the value that should alert someone.
  3. Senior+ Says how a change rolls out safely.
  4. Staff+ Says how cost is watched or kept in bounds.
11

Driving

Leads the interview: sets the order, moves on, and checks in without being prompted.

  1. JuniorMoves on to the next part without being asked, and says which part they are starting.
  2. Mid+ States the order they will cover the design in, before designing.
  3. SeniorNot judged at Senior.
  4. StaffNot judged at Staff.
12

Communication

Makes the design legible: a clear Canvas and explanations the interviewer can follow.

  1. JuniorOn the final canvas, every box is named and joined to its flow.
  2. Mid+ Talks while drawing: names each box as it goes down.
  3. Senior+ Walks the whole design once, near the end.
  4. Staff+ Answers each question in its first sentence, then gives the detail.

Find out where you are.

Thirty minutes out loud, then a Report against the bar you pick.

Private beta · 30 free minutes when you're in