# ConcurrencyMode

Concurrency modes for transactions in Cloud Firestore.

| Enums ||
|---|---|
| `CONCURRENCY_MODE_UNSPECIFIED` | Unspecified. |
| `PESSIMISTIC` | Pessimistic concurrency. |
| `OPTIMISTIC` | Optimistic concurrency. |
| `OPTIMISTIC_WITH_ENTITY_GROUPS` | Optimistic concurrency with entity groups. |