mongodb-dba-patterns

name	mongodb-dba-patterns
confidence	medium
description	MyBlog-specific MongoDB operations guidance for Aspire-managed local runtime, MongoDB.EntityFrameworkCore mappings, repository ownership, and shared-environment DBA work that still needs explicit review before production use.

MongoDB DBA Patterns (MyBlog)

Why this exists

MyBlog runs MongoDB through .NET Aspire and MongoDB.EntityFrameworkCore, not through hand-written driver repositories. This skill narrows MongoDB guidance to real MyBlog code paths so Sam, Gimli, Boromir, and Frodo know which changes are live conventions versus future-only operator notes.

Current MyBlog MongoDB map

Area	Canonical files	Owner	Current rule
Local runtime wiring	src/AppHost/AppHost.cs, src/Web/Program.cs	Boromir + Sam	AppHost defines mongodb and database myblog; Web consumes it through AddMongoDBClient("myblog").
EF Core mapping	src/Web/Data/BlogDbContext.cs	Sam	BlogPost maps to collection blogposts; Version is the optimistic concurrency token.
Repository layer	src/Domain/Interfaces/IBlogPostRepository.cs, src/Web/Data/MongoDbBlogPostRepository.cs	Sam	Repositories return domain entities; handlers wrap results in Result / Result<T>.
Read-side caching	src/Web/Features/BlogPosts/List/GetBlogPostsHandler.cs, src/Web/Features/BlogPosts/Edit/EditBlogPostHandler.cs	Sam	Mongo-backed reads are cached at handler level, not in the repository.
Integration proof	tests/Integration.Tests/Infrastructure/MongoDbFixture.cs, tests/Integration.Tests/BlogPosts/MongoDbBlogPostRepositoryTests.cs	Gimli	Testcontainers-backed Mongo is the canonical verification path for persistence behavior.
Secrets / external hardening	runtime config + deployment pipeline	Frodo + Boromir	User Secrets / secret stores own credentials; never commit connection strings with secrets.

Use this skill when

• changing Mongo wiring in Aspire AppHost or Program.cs
• changing collection mapping, concurrency tokens, or document shape
• diagnosing slow repository reads or missing index support
• planning backups, restores, or Mongo version upgrades for a shared environment
• tightening Mongo authentication, TLS, or least-privilege access
• investigating Mongo-backed integration test failures

MyBlog operational rules

1. Use Aspire for local Mongo first.

   • Start from src/AppHost with dotnet run.
   • Do not hard-code a local Mongo connection string in appsettings.json just to bypass Aspire.

2. Change schema shape in code, not in ad hoc shell sessions.

   • Collection name, concurrency, and entity shape live in BlogDbContext + BlogPost.
   • If a Mongo admin step is required, document it beside the code change and hand it to Boromir for environment rollout.

3. Repository work stays EF Core-first.

   • MongoDbBlogPostRepository uses short-lived contexts from IDbContextFactory<BlogDbContext>.
   • Do not introduce raw IMongoCollection<T> usage unless the EF provider cannot express the query and Sam explicitly signs off.

4. Handler caching remains outside the repository.

   • Query caches belong in MediatR handlers.
   • Any Mongo change that affects list/detail reads must also review cache keys and invalidation in the handler layer.

5. Integration tests are the contract check.

   • Mongo persistence, ordering, and concurrency changes require matching updates in Integration.Tests.
   • Gimli owns the test side; Sam owns runtime implementation.

Local development and inspection

Preferred tooling:

• MongoDB for VS Code or MongoDB Compass for collection inspection, indexes, and explain plans
• Aspire dashboard for connection/runtime visibility
• mongosh only when GUI tooling cannot answer the question

Example inspection flow for MyBlog:

cd src/AppHost
dotnet run

Then connect with the connection string surfaced by Aspire and inspect the live myblog.blogposts collection. For test failures, use the connection string from MongoDbFixture and the per-test database name created in the test.

Collection and mapping conventions

Current canonical mapping:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    var entity = modelBuilder.Entity<BlogPost>();
    entity.ToCollection("blogposts");
    entity.HasKey(p => p.Id);
    entity.Property(p => p.Version).IsConcurrencyToken();
}

Rules:

• Keep collection names lowercase and stable once data exists.
• Treat Version concurrency behavior as part of the storage contract.
• If document shape changes, update the entity, mapping, repository usage, and integration tests in the same change.

Backup and restore guidance

MyBlog has no automated backup workflow in-repo today. Local Aspire and Testcontainers databases are disposable; backup guidance matters only for a shared or production Mongo environment.

If a shared environment is introduced, Boromir owns automation and Sam verifies collection-level restore assumptions.

Example commands for a future shared environment:

mongodump --uri="<shared-mongo-connection-string>" \
  --db=myblog \
  --out=./backups/mongo/2026-04-19

mongorestore --drop \
  --uri="<staging-mongo-connection-string>" \
  --db=myblog \
  ./backups/mongo/2026-04-19/myblog

Rules:

• Never treat disposable local/Testcontainers data as a backup source.
• Always rehearse restore on a non-production target before calling a backup strategy complete.
• Keep backup credentials out of scripts committed to the repo.

Performance and index review

Current read hotspot:

• MongoDbBlogPostRepository.GetAllAsync() sorts by CreatedAt descending.
• GetBlogPostsHandler caches the DTO list in memory + Redis.

MyBlog rules:

• Any new filter or alternate sort added to the repository triggers an index review for blogposts.
• Sam proposes index shape; Gimli verifies the query path with integration tests; Boromir applies/shared-environment rollout when needed.
• Use Compass / VS Code explain plans before adding driver-only code.

Recommended current review candidate if the list grows materially:

db.blogposts.createIndex({ CreatedAt: -1 }, { name: "idx_blogposts_created_desc" })

This is a candidate, not a declared current production index.

Security and secret handling

• Local credentials belong in User Secrets or Aspire-managed secrets, never in committed appsettings*.json values with real secrets.
• Shared-environment Mongo should use SCRAM auth and TLS.
• Frodo reviews least-privilege requirements before any non-local Mongo rollout.
• Do not log raw connection strings, passwords, or certificates.

Package and upgrade guidance

MyBlog pins Mongo packages directly in src/Web/Web.csproj today:

• Aspire.MongoDB.Driver
• MongoDB.EntityFrameworkCore

Upgrade rules:

1. Upgrade one major MongoDB server version at a time.
2. Check the EF Core provider release notes before bumping package versions.
3. Re-run repository integration tests, especially ordering and concurrency.
4. Treat provider upgrades as Sam-owned code work plus Boromir-owned environment coordination.

Explicit non-fit items for later deletion review

The imported skill carried guidance that is not part of normal MyBlog flow yet:

• Manual replica-set initiation steps — local MyBlog uses Aspire and Testcontainers; we do not manually bootstrap replica sets in normal work.
• IssueManager collection examples — not part of this repo and removed from the retained guidance.
• Atlas-only cluster administration detail — useful only if MyBlog adopts a managed shared Mongo deployment later.
• Always-on profiling guidance — premature for the current small training app; only use profiling during a targeted investigation.

If MyBlog stays Aspire-local and test-container-only, revisit whether the shared-environment backup/upgrade sections should be trimmed further in Milestone 3.

References

• src/AppHost/AppHost.cs
• src/Web/Program.cs
• src/Web/Data/BlogDbContext.cs
• src/Web/Data/MongoDbBlogPostRepository.cs
• tests/Integration.Tests/Infrastructure/MongoDbFixture.cs
• MongoDB EF Core Provider
• MongoDB for VS Code
• mongodump / mongorestore