Everything Wrong with Firestore

nuances, missing features, strange API, things to watchout, and wishlist

Types

• Firestore does not work with custom types, it requires marshalling to JSON and unmarshalling to map[string]any before writing to Firestore
• Firestore does not support uint64
• Firestore needs manual setting into map[string]any time.Time values after decoding before write to Firestore so that Firestore recognizes time.Time type
• firestore.Increment(1) on new field will have float64 type, not int64

Iterator

• Firestore iterator has no backoff mechanism
• Firestore iterator may return Unavailable gRPC status, yet never terminate
• Firestore iterator may never terminate
• Firestore iterator cannot iterate over whole collection, it requires reading docs in batches (index, and order_by does not help)

Update()

• Firestore Update() silently fails when some fields are not mutated (e.g. JSON path mistake)
• Firestore Update() cannot ovewrite field of array type
• Firestore cannot Update() field multiple times in the same operation (e.g. cannot ArrayRemove and ArrayUnion in the same operation)
• Firestore cannot Update() n-th element in array in field (e.g. $.receipt.products[0].category is not possible to udpate)

JSON Path

• Firestore cannot Set() field by JSON path (e.g. "product.gtin": ... will be stored as a field product.gtin in root, instead do "product": map[string]any{"gtin": ...})
• Firestore cannot Update() field by JSON path, it has to be through Set() with MergeAll

Monitoring

• Firestore option.WithTelemetryDisabled() does not disable telemetry. bug is reported and not fixed for 5+ months. as of 2026-02-22 still not fixed.
• Firestore sets trace span names with id in them, resulting in polluting traces with garbage and high cardinality and cost. you would get something like /my_collection/_doc/asdf1234 traces of kind client. bug is reported and not fixed for 6+ months. as of 2026-02-22 still not fixed.