Coinbase OA

Cloud Compute Credits System

Implement a simplified cloud compute credits system.

All operations have a timestamp parameter representing a timestamp in milliseconds.

All timestamps are unique.
1 <= timestamp <= 10^9
Operations are given in strictly increasing timestamp order.
Level 1 — Workspace Management and Credit Transfers

Initially, the system contains no workspaces.

The system should support creating workspaces, adding credits to workspaces, and transferring credits between workspaces.

boolean createWorkspace(int timestamp, String workspaceId)

Creates a new workspace with the given identifier.

Requirements:

The newly created workspace has an initial credit balance of 0.
Return true if the workspace is successfully created.
Return false if a workspace with the same workspaceId already exists.
Optional<Integer> topUp(int timestamp, String workspaceId, int amount)

Adds amount credits to the specified workspace.

Requirements:

If workspaceId does not exist, return Optional.empty().
Otherwise, add amount to the workspace's balance.
Return the workspace's balance after the top-up.
Optional<Integer> transferCredits(int timestamp, String sourceWorkspaceId, String targetWorkspaceId, int amount)

Transfers amount credits from the source workspace to the target workspace.

Return Optional.empty() if:

sourceWorkspaceId does not exist.
targetWorkspaceId does not exist.
sourceWorkspaceId and targetWorkspaceId are the same.
The source workspace has insufficient credits.

Otherwise:

Deduct amount from the source workspace.
Add amount to the target workspace.
Return the source workspace's remaining balance.
Level 2 — Rank Workspaces by Outgoing Credits

The platform wants to identify workspaces that drain their credits quickly.

The system should support ranking workspaces according to their total outgoing credit transactions.

List

您好！
本帖隐藏的内容需要积分高于 188 才可浏览
您当前积分为 0。
使用VIP即刻解锁阅读权限或查看其他获取积分的方式

游客，您好！
本帖隐藏的内容需要积分高于 188 才可浏览
您当前积分为 0。
VIP即刻解锁阅读权限 或 查看其他获取积分的方式
Unlock interview details and practice with AI
Curated Interview Questions from Top Companies

, 20) → 900

If no operation happened exactly at timeAt, return the balance resulting from the most recent operation before timeAt.

Workspace existence at timeAt

If the specified workspace did not exist at timeAt, return:

Optional.empty()

This applies in two situations.

If queried before creation:

t=10 create workspaceA


getCredits(..., "workspaceA", 5)
→ Optional.empty()

If queried after that workspace was merged away:

t=10 create workspaceB
t=30 merge B into A


getCredits(..., "workspaceB", 20)
→ B's balance at t=20


getCredits(..., "workspaceB", 30)
→ Optional.empty()


getCredits(..., "workspaceB", 40)
→ Optional.empty()

So even though workspaceB is no longer active, its pre-merge historical balance must remain queryable.

Merge and balance history

A merge affects the surviving workspace starting at the merge timestamp, not retroactively.

For example:

t=10:
A = 1700
B = 600


t=20:
merge B into A

Then:

getCredits(..., "A", 15)
→ 1700


getCredits(..., "B", 15)
→ 600


getCredits(..., "A", 20)
→ 2300


getCredits(..., "B", 20)
→ Optional.empty()

This distinction is especially important: B's old balance must not be added retroactively to A's pre-merge history.