# Node SDK v5.x.x to v6.0.0 Upgrade Guide

### Summary

Node.js SDK V6.0.0 introduced breaking changes on

* [Removed async version of core APIs (checkGate, getConfig..)](#synchronous-core-apis)
* [Changed DataAdapter cache keys SDK used to read and write from](#dataadapter-cache-key-changes)
* [Changed default hashing algorithm used for getClientInitializeResponse() which is being used for bootstrapping client sdk.](#hash-algorithm-change-on-getclientinitializeresponse)
* [If no environment tier is set for the SDK, the environment defaults to `production` when evaluating.](#default-environment-is-production-if-no-environment-is-being-set-when-sdk-is-initialized)
* [Changed how you should disable exposure logging](#deprecate-functions)

#### Synchronous core APIs

**Changes**
Changed all core apis to be synchronous functions

```javascript
// All removed
async getFeatureGate(): Promise<FeatureGate> // Removed
getFeatureGate(): FeatureGate // New API

async checkGate(): Promise<bool> // Removed
checkGate(): bool // New API

async getConfig(): Promise<DynamicConfig>
getConfig(): DynamicConfig // New API

async getExperiment(): Promise<DynamicConfig>
getExperiment(): DynamicConfig // New API

```

**Context**
The original async API design ensured that every evaluation could complete correctly, even when the SDK wasn't compatible, by requesting evaluation from the Statsig server. As the SDK and evaluation rules became more stable, you rarely need this fallback. All APIs are now synchronous to improve performance.

**Migration Guide**
If you're using JavaScript and call a gate like this, a runtime error occurs. Audit and update your usage. If you're using TypeScript, the compiler reports an error instead.

The `*Sync()` functions (for example, `checkGateSync()`) are deprecated. Use `checkGate()` instead.

```javascript
Statsig.checkGate(user, "gate").then(() => {
  // do somethig
}).catch() // Compile error if you are using typescript. If you are using javascript, there will be runtime error please audit and 
```

If you're using `await` like this, Statsig recommends removing it, but it continues to work.

```javascript
const gate = await Statsig.checkGate(user, "gate")
```

#### DataAdapter cache key changes

**Context**
To better support multiple Statsig instances in one runtime and different response formats (for example, `download_config_spec_v1` vs `download_config_spec_v2`), Statsig updated the cache keys the SDK reads and writes from. The new keys avoid cache key collisions. The SDK also embeds the compress encoding format in the key. The SDK stores only the plain-text uncompressed version in cache.

**Changes**

* Change cache key for config\_specs from `statsig.cache` to

`statsig|/v1/download_config_specs|{compressEncoding // plain text for now}|{SHA256HashedBase64(secretkey)}`

* Change cache key for get\_id\_list\_sources from `statsig.id_lists` to be:

`statsig|/v1/get_id_lists|{compressEncoding // plain text for now}|{SHA256HashedBase64(secretkey)}`

* Change cache key for individual id list to be

`statsig|id_list::$\{String(idListName)\}|\{compressEncoding // plain text for now\}|${SHA256HashedBase64(secretKey)}`

**Migration Guide**

{% callout type="warning" %}
If you're using one of the Edge DataAdapters, don't upgrade yet. Statsig is adding support for this.
{% /callout %}

1. Update your DataAdapter if you have customized the key, get, or read logic.
2. If you write to cache in other places (instead of relying on the SDK to set the cache), update the call site to use the new key.
3. If a cache miss on the first request is acceptable, you don't need to do anything. The SDK writes to cache with the new key automatically.
4. To avoid a cold cache, write with the new key before deploying to production.

#### Hash algorithm change on getClientInitializeResponse()

**Context**
To improve evaluation speed on both client and server and reduce payload size, the default hash algorithm for all config names changed from SHA256 to djb2.

**Changes**
The SDK now hashes config names (gates, experiments, layers) with djb2 by default. If you specify a hash algorithm explicitly, this change doesn't affect you.

**Migration Guide**
If you're using a recent client SDK version, client-side support is automatic and you don't need to do anything. To continue using SHA256, set `ClientInitializeResponseOptions.hash = 'sha256'`.

#### Default environment is production if no environment is being set when SDK is initialized

**Context**
The environment tier setting caused frequent confusion.

**Changes**
If you don't set an environment tier (for example, `StatsigOptions.environment.tier`), the SDK now assigns a default value. If you set the SDK key, the SDK uses that; otherwise the SDK defaults to production.

**Migration**
Call sites that don't set an environment tier now fail rules that target non-production environment tiers. Call sites that set an environment tier, or rules that don't set an environment or include the production tier, are unaffected.

#### Deprecate functions

The `WithExposureLoggingDisabled` functions are deprecated:

```javascript
checkGateWithExposureLoggingDisabled()  // DO NOT USE
getFeatureGateWithExposureLoggingDisabled() // DO NOT USE
```

Use core APIs with options instead:

```javascript
Statsig.checkGate(user, gate_name, {disableExposureLogging: true})  // Use
Statsig.getFeatureGate(user, gate_name, {disableExposureLogging: true})  // USE
```