Flexport Software Engineer
Interview Guide

• Take the reported container yard prompt: list entities (Container, Yard or Slot, ClientAccount, Order with a buy or sell side), their state and public methods before any code.
• Implement it in three phases without rewriting earlier code: store and remove containers, then client balances, then matching buy and sell orders. Note every place a phase forced an edit.
• Take the card and token purchasing prompt: model Card (cost per color, points, color), Player (tokens, per-color discounts), and a canPurchase that subtracts discounts from cost with a floor of zero before checking tokens.
• Say your class design out loud before coding each prompt, as you would in the room.

Deliverable: Two phased OOD solutions, plus a list of the edits each new phase forced and how you would design to avoid them.

• Build the freight rate calculator with pricing tiers, volume discounts and currency conversion as separate components. Store money as integer minor units or a decimal type, never floats.
• Build the Connect-N engine so a move only checks lines through the last piece: count matching pieces in both directions along each axis (4 line directions in 2D, 13 in 3D).
• Extend each solution with one requirement you did not plan for (a new discount rule, a new board dimension) and measure how much existing code you had to change.
• Review each solution out loud: naming, edge cases (empty board, full column, zero volume) and the refactor you would make next.

Deliverable: Two extensible solutions with a short list of the edge cases each handles and the one refactor you would do next.

• Grid path queries: label connected components once with BFS or union-find, then answer each query in O(1). Write out the complexity before and after precomputing.
• Flood fill: mark all land reachable from the boundary cells, then submerge every unmarked island. Test a grid with no boundary land and a grid that is all land.
• Meeting rooms or docking bays: solve with a min-heap of end times and again with sorted start and end arrays. Decide whether an end equal to a start counts as overlap. Pair with the bank question on meeting coverage and required rooms.
• Write a max-heap with sift-up and sift-down, and a weighted dice roller using prefix sums plus binary search.

Deliverable: Four solutions with stated complexity and one test each for the edge case most likely to break them.

• Phone number to strings where keys can take multi-digit inputs: solve with backtracking over how the digits split up, then note where memoization pays off.
• Restore IPv4 addresses from a digit string (bank topic): backtrack over the dot positions, reject segments above 255 and segments with leading zeros.
• Practice the classic house-robber DP, first the linear version in O(n) and then the circular version, as preparation for the bank topic on two robbery optimization variants.
• Target-word guessing (bank topic): pick each guess to minimize the size of the worst-case group of remaining candidates, and explain why that bounds the number of guesses.

Deliverable: Four solved problems, each with its recurrence or pruning rule written above the code.

• Design a reservation system in the style of the reported OpenTable-style prompt: endpoints, schema, availability search, and the exact mechanism that prevents double booking. Use the drill on allocating stock on hot item-node pairs to practice the throughput ceiling of a single hot row.
• Design the GPS tracking aggregator for trucks and vessels: ingestion stream partitioned by vehicle, separate latest-position and history stores, and out-of-order handling as in the SQL drill on folding late, out-of-order scan events.
• Work through the carrier gateway worked exercise (booking carriers at most once through timeouts) and run its checks against your own answer.
• Sketch the bank design topic on assigning containers when some goods cannot share a container: the data model, the assignment rule, and what happens when no valid assignment exists.

Deliverable: Two full designs with APIs, schemas and a concurrency story, plus notes on the carrier gateway worked exercise.

• Complete the worked SQL exercise on ledger and position reconciliation, including every check it lists.
• Write the event-time fold from the late, out-of-order scan events SQL drill and show that replaying the events in shuffled order gives the same result.
• Complete the worked coding exercise on parsing partner quantity and date segments without floating point, and grep your parser for float types.
• Diagnose the frozen-partner-feed debugging drill out loud in order: prove ingestion is healthy, classify the error, then park the poison message.

Deliverable: Two SQL queries that pass their checks, one integer-only parser, and a written diagnosis sequence for the stalled partition.

• Prepare the project deep dive: a block diagram you can redraw, the path one request takes through it, three defended decisions, and what you would change today.
• Write stories for the reported behavioral themes: leading a project from scratch, a project that went off track, quality versus deadlines, and a technical disagreement.
• Run a mock of one multi-part OOD prompt from days 1 and 2 with a partner who adds a new requirement partway through.
• List the weakest area from the week and redo one problem from it without notes.

Deliverable: A rehearsed deep dive, four behavioral stories, and notes from one mock with a mid-problem requirement change.