Drills

Implement an optimistic version conflict in JPA

Carries the version observed by the client into a conditional update and returns an explicit conflict instead of silently overwriting newer data.

JavaSpring Boot

Implement a persisted idempotent FastAPI POST

Implements a database-backed idempotency boundary that replays one response and rejects key reuse with a different request.

FastAPIPythonSQLAlchemy

Implement a persisted idempotent POST

Stores an idempotency key, request hash, and response in the same transaction as the created resource.

Implement a stable EF Core keyset page

Implements descending keyset pagination in LINQ using a compound timestamp-and-id cursor.

.NETASP.NET CoreNext.jsReactSQL Server+1

Implement debounced search and request cancellation

Explains debounce, cancellation, stale-response protection, loading indicators, and backend query safety for search UI.

Implement keyset pagination with EF Core

Explains stable EF Core pagination using cursor predicates, deterministic ordering, and index-aligned queries.

Implement stable keyset pagination with async SQLAlchemy

Builds descending keyset pagination with a unique tie-breaker, opaque cursor, limit-plus-one query, and stable next page.

PythonSQLAlchemy

Implement stable keyset pagination with Spring Data JPA

Implements descending cursor pagination with a unique tie-breaker, bounded projection query, and next-cursor detection.

JavaSpring Boot

Import records in bounded EF Core batches

Processes a large import in chunks with fresh DbContexts, idempotent keys, cancellation, and bounded tracker growth.

.NETASP.NET CoreC#EF Core

Ingest a webhook safely and idempotently

Verifies the exact request bytes, rejects stale signatures, deduplicates event ids, and queues processing durably.

Inspect generated SQL before tuning an EF Core query

Explains how to inspect EF Core generated SQL and connect LINQ shape to database execution behavior.

Debugging scenarioHard~12 min

Investigate a slow EF Core query in production

Investigates a growing-data EF Core slowdown through one correlated request, generated SQL, representative parameters, execution plan, waits, query shape, measured repair, and guarded rollout.

.NETApplication InsightsASP.NET CoreEF CoreSQL+1

Know when to use raw SQL or Dapper instead of EF Core LINQ

Explains when LINQ is enough, when raw SQL is clearer, and how to keep raw SQL safe and maintainable.

Load a tracked aggregate with a split query

Uses `AsSplitQuery` deliberately for a tracked aggregate with multiple collections and explains its consistency boundary.

Map a unique email race to a conflict response

Relies on a database unique constraint and translates only the expected provider error into a domain conflict.

Comparison questionMedium~7 min

Modular monolith vs microservices

Chooses between a modular monolith and microservices using domain boundaries, team ownership, scaling, deployment, data consistency, and operational cost.

.NETASP.NET CoreSQL Server

Concept questionHard~9 min

Page orders with a stable keyset cursor

Implements descending keyset pagination with a compound cursor and stable ordering.

SQLSQL Server

Plan a safe schema migration without downtime

Explains expand-and-contract migrations, backwards-compatible schema changes, backfills, rollout order, and rollback thinking.

SQLSQL Server

.NETASP.NET CoreNext.jsReactSQL Server+1

Prevent double submits and duplicate mutations

Explains frontend guards, backend idempotency, pending state, retries, and duplicate-safe mutation design.

Prevent overposting with an explicit update DTO

Updates only public mutable fields and leaves ownership, status, and audit values server-controlled.

.NETASP.NET CoreC#

Project an EF Core query into an API DTO with nested summary data

Explains EF Core projections for API read models that need related names, counts, and summaries without loading full graphs.

Project an order list directly into a DTO

Builds a read-only EF Core projection with aggregates, stable ordering, and bounded results instead of loading an entity graph.

Propagate request cancellation through an EF Core query

Carries the ASP.NET Core request token into a bounded EF Core query while keeping cancellation separate from business rollback guarantees.