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Implement a user profile service

This topic describes how to set up a custom User Profile Service or how to use the default for the Optimizely Go SDK.

Use a User Profile Service to persist information about your users and ensure variation assignments are sticky. The User Profile Service implementation you provide will override Optimizely's default bucketing behavior in cases when an experiment assignment has been saved.

When implementing in a multi-server or stateless environment, we suggest using this interface with a backend like Cassandra or Redis. You can decide how long you want to keep your sticky bucketing around by configuring these services.

Implementing a User Profile Service is optional and is only necessary if you want to keep variation assignments sticky even when experiment conditions are changed while it is running (for example, audiences, attributes, variation pausing, and traffic distribution). Otherwise, the Go SDK is stateless and relies on deterministic bucketing to return consistent assignments.

If the User Profile Service doesn't bucket a user as you expect, then check whether other feature flags are overriding the bucketing. For more information, see How bucketing works.

Implement a user profile service

Refer to the code samples below to provide your own User Profile Service. It should expose two functions with the following signatures:

  • lookup: Takes a user ID string and returns a user profile matching the schema below.
  • save: Takes a user profile and persists it.
import ( "github.com/optimizely/go-sdk/pkg/decision" )

// CustomUserProfileService is custom implementation of the UserProfileService interface
type CustomUserProfileService struct {

// Lookup is used to retrieve past bucketing decisions for users
func (s *CustomUserProfileService) Lookup(userID string) decision.UserProfile {
   return decision.UserProfile{}

// Save is used to save bucketing decisions for users
func (s *CustomUserProfileService) Save(userProfile decision.UserProfile) {

The UserProfile struct

type UserProfile struct {
   ID                  string
   ExperimentBucketMap map[UserDecisionKey]string

// UserDecisionKey is used to access the saved decisions in a user profile
type UserDecisionKey struct {
   ExperimentID string
   Field        string

// Sample user profile with a saved variation
userProfile := decision.UserProfile{
        ID: "optly_user_1",
        ExperimentBucketMap: map[decision.UserDecisionKey]string{
            decision.UserDecisionKey{ExperimentID: "experiment_1", Field: "variation_id" 
    }: "variation_1234",

Use experiment_bucket_map from the UserProfile struct to override the default bucketing behavior and define an alternate experiment variation for a given user. For each experiment that you want to override, add an object to the map. Use the experiment ID as the key and include a variation_id property that specifies the desired variation. If there isn't an entry for an experiment, then the default bucketing behavior persists.

The Go SDK uses the field variation_id by default to create a decision key. Create a decision key manually with the method decision.NewUserDecisionKey:

decisionKey := decision.NewUserDecisionKey("experiment_id")

Passing a User Profile Service Implementation to the OptimizelyClient:

userProfileService := new(CustomUserProfileService)
optimizelyClient, err := factory.Client(