XcelCrowd
For CompaniesSign InSign Up

Build real things.
Prove you can engineer.

Companies post real engineering problems. You solve them. We evaluate your code, your commits, and your design decisions. Top profiles get found by hiring teams.

Start your first build

Free to start. No credit card.

Portfolio projects

You built a to-do app and a weather dashboard. So did 50,000 other students. You built real things — but nobody saw the engineering behind them. No review. No score. No proof it was your thinking.

Certificates & courses

You completed 14 certification courses and have DSA badges. So does everyone who paid ₹399 and followed along. It proves you can follow instructions, not that you can engineer.

Campus placements

You submitted your resume to 30 companies through your college. HR screened it for 7 seconds, couldn't tell you apart from 200 others, and you never heard back.

The problem isn't your skill. It's that nothing you're doing right now actually proves it.

How it works

Here's what actually works. Three steps. No resumes. No algorithm quizzes.

Step 01

Pick a build

Browse open builds posted by real companies. Each one is a real engineering problem — not a DSA puzzle or a tutorial project.

Step 02

Push your solution

Work in your own IDE. When you’re done, submit your GitHub repo. That’s the entire submission process.

Step 03

Get your review

XVal evaluates your code and how you built it. You get scores across seven engineering dimensions, written feedback, and where you rank.

This is what your review looks like

Every submission gets this. Score 92 or 43, you walk away knowing exactly where you stand and what to work on next.

Stealth Fintech Startup

Payment Reconciliation Service

74/100
#3/17·Top 18%

Score Breakdown

Base Score+100
Requirement Penalties-8
Quality Penalties-23
Bonuses+7
Final Score74

You kept the reconciliation logic separate from each payment provider, which is the right call. If you ever need to swap out Stripe for a new provider, you only change one file. One thing to work on: you wrote the retry logic three times, once per provider. Pull that into a shared function so you only have to maintain it in one place.

Code Originality

independentConfidence: high

Architecture reflects deliberate domain-driven design. Standard Express/TypeScript patterns adapted to the reconciliation domain without unnecessary scaffolding.

What to improve

  • •You wrote retry logic three times (StripeAdapter.ts:61, PayPalAdapter.ts:44, SquareAdapter.ts:52). Pull it into one shared function so changes apply everywhere.
  • •Your tests cover individual adapters but not what happens when a batch fails halfway through. Add an integration test that simulates one provider going down mid-batch.

Build & Test

Partial
Install DependenciesPassed8.2s
Build / CompilePassed4.1s
Run TestsFailed6.1s

6 of 8 tests passed. 2 failures in batch processing suite.

Code Quality

Readability
good
  • –Variable names in BatchProcessor.ts use abbreviations (txn, rcn) that reduce scannability
  • +Consistent file structure across all service modules with clear separation of imports, types, and logic
  • +TypeScript interfaces defined close to usage rather than in a central types file — good colocation
Error Handling
good
  • –Bare catch blocks in BatchProcessor.ts:92 swallow errors silently during batch retries
  • +Typed error hierarchy (ReconciliationError, GatewayTimeoutError) enables precise recovery per failure mode
  • +Gateway adapters propagate error context up the call chain cleanly
Testing
fair
  • –No integration tests for concurrent batch processing — tests/ covers individual adapter units only
  • –Test fixtures hardcode gateway responses instead of using factory patterns
  • +Unit tests cover core reconciliation logic with good edge case coverage for individual adapters

Design Quality

Architecture
good
  • –BatchProcessor imports concrete adapter classes — no dependency injection
  • +Clean bounded contexts between reconciliation, gateway, and discrepancy domains
  • +Adapter pattern in src/types/GatewayAdapter.ts enables zero-downtime provider rotation
Abstractions
fair
  • –Retry logic duplicated across StripeAdapter.ts:61, PayPalAdapter.ts:44, SquareAdapter.ts:52
  • –Configuration values scattered across files instead of centralized env config
  • +Gateway adapter interface is well-abstracted with clear contract boundaries
Data & API Design
excellent
  • +Compound unique indexes in src/models/Transaction.ts prevent duplicate reconciliation entries across restarts
  • +API routes follow RESTful conventions with proper HTTP semantics
  • +Database schema normalizes gateway-specific fields without over-engineering the shared model
Complexity Balance
good
  • –DiscrepancyDetector could be simplified by using event emitter pattern instead of manual callback chain
  • +Solution complexity matches problem scope — no unnecessary abstraction layers

Review Summary

You kept the reconciliation logic separate from each payment provider, which is the right call. If you ever need to swap out Stripe for a new provider, you only change one file. One thing to work on: you wrote the retry logic three times, once per provider. Pull that into a shared function so you only have to maintain it in one place.

Strengths

  • •Each payment provider has its own adapter file with a shared interface. This means adding a new provider is one new file, not a rewrite.
  • •Your transactions table uses unique indexes to prevent duplicates. If the service crashes mid-reconciliation and restarts, it picks up without creating double entries.
  • •You created specific error types like ReconciliationError and GatewayTimeoutError. This makes it easy to handle each failure case differently instead of catching everything with a generic handler.

Areas for Improvement

  • •You wrote retry logic three times (StripeAdapter.ts:61, PayPalAdapter.ts:44, SquareAdapter.ts:52). Pull it into one shared function so changes apply everywhere.
  • •Your tests cover individual adapters but not what happens when a batch fails halfway through. Add an integration test that simulates one provider going down mid-batch.
  • •Timeout values are hardcoded in PayPalAdapter.ts:47 and StripeAdapter.ts:83. Move these to environment config so you can tune them without redeploying.

Key Issues

majorRetry logic written separately in each of the 3 payment adapters with different backoff strategies

src/adapters/StripeAdapter.ts:61, PayPalAdapter.ts:44, SquareAdapter.ts:52

→ Create a shared withRetry() function with configurable backoff. All three adapters should use it.

In production payment systems, retry logic is shared infrastructure. When it is duplicated, the copies drift apart over time and bugs only get fixed in one place.

majorNo tests for what happens when a payment provider fails during a batch

tests/adapters/

→ Write a test where one provider goes down mid-batch. Make sure the transactions that already went through are safe.

Partial batch failures are the most common failure mode in payment systems. Testing for them is not optional.

minorBatchProcessor directly imports each adapter class instead of receiving them as parameters

src/handlers/BatchProcessor.ts:12–14

→ Pass adapters into the constructor. This makes testing easier and lets you add new providers without changing BatchProcessor.

This is called dependency injection. It is how production systems stay flexible when new integrations are added.

Multi-gateway reconciliation enginecore

src/services/ReconciliationEngine.ts, src/adapters/StripeAdapter.ts, PayPalAdapter.ts, SquareAdapter.ts

Complete
Real-time discrepancy detectioncore

src/services/DiscrepancyDetector.ts — event-driven flagging within reconciliation loop

Complete
Consistent error recovery across service boundariescore

Typed errors in src/errors/ but bare catch blocks in src/handlers/BatchProcessor.ts:92

Partial
Batch processing with retry semanticssecondary

src/handlers/BatchProcessor.ts — batching works but retry strategy inconsistent across adapters

Complete
API documentation & endpoint specpolish

No OpenAPI spec found — README.md covers features only

Missing
•src/config/defaults.ts:12 — Default timeout value appears hardcoded — consider environment variable

Code Files

18

Avg Lines/File

94

Max File Lines

312

Concentration

14%

Folder Depth

4

Comment Ratio

0.06

Used AI tools? Good. We evaluate your engineering decisions, not who typed the code.

Four builds. Four honest reviews.

This is how engineers improve on XcelCrowd.

BuildScoreRankReadabilityError HandlingArchitecture
Build 148Top 61%fairpoorfair
Build 257Top 38%goodfairfair
Build 371Top 19%goodgoodgood
Build 481Top 9%excellentgoodexcellent

Every review shows exactly where you stand and what to work on next.

Start your first build →

Open builds

Real engineering problems from real companies. Pick one and start building.

Stealth Series A Fintech

Payment Reconciliation Service

Design a service that reconciles payment records across multiple gateway providers and flags discrepancies in real time.

Node.jsPostgreSQLEvent-Driven

Stealth B2B SaaS Startup

Multi-Tenant Notification Engine

Build a notification system that supports email, SMS, and in-app channels with per-tenant rate limiting and delivery tracking.

TypeScriptRedisREST API

Stealth D2C Platform

Route Optimization API

Create an API that calculates optimal delivery routes given a set of waypoints, time windows, and vehicle constraints.

PythonFastAPIAlgorithms
View all builds →

Your verified build profile

Every build you complete adds to a profile that companies actually search. Not a resume. Not a certificate. Proof.

ReadabilityError HandlingTestingArchitectureAbstractionsData & APIDesignComplexityBalance

Based on 5 completed builds

Payment Reconciliation Service

Stealth Fintech Startup

74Good

Top 18%

Multi-Tenant Notification Engine

Series A SaaS Company

81Excellent

Top 9%

Route Optimization API

B2B Logistics Platform

58Fair

Top 32%

Real-Time Chat Backend

EdTech Scale-Up

79Good

Top 12%

Inventory Sync Pipeline

D2C E-Commerce Startup

72Good

Top 22%

Share it. Or let companies find you.

Companies post builds to find engineers to hire. When you rank in their challenge, you're on their shortlist. A company searching for “Node.js engineers with strong architecture” will see your profile. You don't apply. They find you.

Hiring engineers?

Post a real engineering problem. Receive ranked candidates with full evaluation reports and GitHub proof.

Post a challenge →