database · inferred from evidence
MongoDB
A database system from which incremental syncs were failing due to offset issues.
- ModuleNotFoundError: No module named 'langchain_openai' (or any provider package)
This error means the provider package is not installed. LangChain splits every provider into its own package, so installing langchain alone is never enough for OpenAI, Anthropic, or any other model or store.
- Atlas: live-migrate a self-hosted cluster to Atlas with minimal downtime
Atlas Live Migration hosts mongosync for you. Pick pull or push, monitor the sync, then cut over writes in a controlled window.
- Atlas: shard an existing collection safely
Enable sharding on the database, shard the collection with the chosen key, pre-split, and verify distribution before declaring victory.
- Atlas: choose a shard key using cardinality, frequency, and monotonicity
The shard key is the hardest decision in sharding and nearly immutable. Evaluate candidate fields on the three axes before committing.
- Atlas: set up an AWS PrivateLink private endpoint
Private endpoints give you private connectivity without peering CIDR juggling. Create in Atlas, create the interface endpoint in AWS, approve, then switch strings.
- Atlas: diagnose memory pressure and working set overflow
Cache evictions and page faults mean the working set exceeds RAM. Confirm with FTDC-style metrics, then reduce the working set or scale up.
- Atlas error: BSON document exceeds the 16MB limit
Documents have a hard 16MB cap. Hitting it means the schema needs chunking, references, or GridFS, not a bigger limit.
- Atlas error: WriteConflict inside a transaction
Two transactions wrote the same document and one lost. This is normal concurrency control, not corruption. Retry the whole transaction.
- MongoDB Atlas: Mongoose connection setup that survives deploys
Mongoose adds buffering and model-level traps on top of the driver. This skill covers connect options, bufferCommands behavior, and why you must not call mongoose.connect per request.
- MongoDB Atlas: connect the Node.js driver with one shared MongoClient
The Node.js driver wants one MongoClient per app, created once and reused. This skill covers the Atlas SRV string, the pool options that matter, and the per-request client trap that exhausts connections.
- Atlas error: TLS handshake failure connecting to the cluster
Atlas requires TLS. These errors mean the client and server disagreed about encryption. Never fix them by disabling verification.
- Atlas error: ServerSelectionTimeoutError, no suitable servers
The driver cannot reach any cluster node. On Atlas this is the IP access list nine times out of ten. Check that before anything else.
- MongoDB Atlas: copy the connection string without breaking it
Half of all Atlas connection failures are a mangled connection string: wrong password placeholder, unencoded special characters, wrong form. This skill makes the copy exact.
- MongoDB Atlas: size the connection pool deliberately
Default pool settings are fine until they are not. This skill gives the sizing math and the metrics to watch.
- MongoDB Atlas: connect from AWS Lambda and Vercel without pool exhaustion
Serverless functions scale to hundreds of concurrent executions, each wanting connections. This skill covers client reuse and small pools.
- MongoDB Atlas: query with $vectorSearch correctly
$vectorSearch must be the first pipeline stage and has specific knobs. This skill covers numCandidates, limit, filters, and scoring.
- MongoDB Atlas: retryWrites, write concern, and read preference that work
Transactions silently need retryWrites and primary reads. This skill sets the three options correctly and explains what breaks when they are wrong.
- MongoDB Atlas: pick mongodb+srv or the standard connection string
Agents default to the SRV string and get stuck on DNS failures or private networking. This skill says when to use each form and how to fall back.
- MongoDB Atlas: Java sync driver connection settings
The Java driver wants a ConnectionString or MongoClientSettings and try-with-resources cleanup. This skill gives the Atlas-ready pattern.
- Preview feature feedback: jsonProtocol
A practical guide for Prisma. Prisma's jsonProtocol preview feature (available since 4.11.0) replaces the GraphQL-based query protocol with JSON, cutting client init time and memory noticeably (the thread's benchmarks show ~80-95% faster Pr