Querying Genesys Cloud LLM Gateway API Usage Costs with Go

What You Will Build

• A Go module that constructs and validates LLM Gateway usage cost queries, executes atomic HTTP GET requests with retry and pagination, processes token aggregation and currency conversion, and synchronizes results with external billing webhooks.
• The implementation uses the Genesys Cloud /api/v2/llm-gateway/usage/costs endpoint and OAuth 2.0 Client Credentials flow.
• The code is written in Go 1.21+ using the standard library, with explicit mappings to the official platformClient and ApiClient SDK patterns.

Prerequisites

• Genesys Cloud OAuth 2.0 Client Credentials grant configured with the llm-gateway:read scope.
• Go runtime version 1.21 or higher.
• Network access to https://api.mypurecloud.com (or your environment domain).
• No external dependencies required. The standard library provides all necessary HTTP, JSON, and concurrency primitives.

Authentication Setup

Genesys Cloud uses OAuth 2.0 for API authentication. You must exchange your client credentials for a bearer token before executing any query. The token expires after twenty minutes, so the implementation includes a caching mechanism and automatic refresh logic.

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"time"
)

type TokenResponse struct {
	AccessToken string `json:"access_token"`
	ExpiresIn   int    `json:"expires_in"`
	TokenType   string `json:"token_type"`
}

func fetchOAuthToken(ctx context.Context, clientID, clientSecret, envDomain string) (TokenResponse, error) {
	url := fmt.Sprintf("https://%s/oauth/token", envDomain)
	payload := fmt.Sprintf("grant_type=client_credentials&client_id=%s&client_secret=%s", clientID, clientSecret)

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, nil)
	if err != nil {
		return TokenResponse{}, fmt.Errorf("failed to create token request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	req.SetBasicAuth(clientID, clientSecret)
	req.Body = nil // Basic auth handles credentials, body is empty for client_credentials

	client := &http.Client{Timeout: 10 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return TokenResponse{}, fmt.Errorf("token request failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return TokenResponse{}, fmt.Errorf("oauth error: status %d", resp.StatusCode)
	}

	var tokenResp TokenResponse
	if err := json.NewDecoder(resp.Body).Decode(&tokenResp); err != nil {
		return TokenResponse{}, fmt.Errorf("failed to decode token response: %w", err)
	}

	return tokenResp, nil
}

The llm-gateway:read scope is required for all subsequent operations. If your client lacks this scope, the API returns a 403 Forbidden response with a scope_not_granted error code.

Implementation

Step 1: Query Payload Construction and Constraint Validation

Before issuing an HTTP request, you must construct the query payload containing the usage-ref reference, llm-matrix filters, and tally directive. You must also validate the payload against llm-constraints and maximum-query-range limits to prevent querying failure.

type LLMMatrix struct {
	Provider string `json:"provider"`
	ModelID  string `json:"model_id"`
	Region   string `json:"region,omitempty"`
}

type TallyDirective struct {
	GroupBy       string `json:"group_by"`
	Aggregate     string `json:"aggregate"`
	Currency      string `json:"currency"`
	AutoTrigger   bool   `json:"auto_trigger_report"`
}

type CostQueryPayload struct {
	UsageRef   string         `json:"usage_ref"`
	LLMMatrix  LLMMatrix      `json:"llm_matrix"`
	Tally      TallyDirective `json:"tally"`
	StartDate  string         `json:"start_date"`
	EndDate    string         `json:"end_date"`
}

type QueryConstraints struct {
	MaximumQueryRangeDays int      `json:"maximum_query_range_days"`
	ValidModelIDs         []string `json:"valid_model_ids"`
}

func validateQueryPayload(payload CostQueryPayload, constraints QueryConstraints) error {
	// Parse dates for range validation
	start, err := time.Parse(time.RFC3339, payload.StartDate)
	if err != nil {
		return fmt.Errorf("invalid start_date format: %w", err)
	}
	end, err := time.Parse(time.RFC3339, payload.EndDate)
	if err != nil {
		return fmt.Errorf("invalid end_date format: %w", err)
	}

	// Validate maximum-query-range limits
	duration := end.Sub(start).Hours() / 24
	if int(duration) > constraints.MaximumQueryRangeDays {
		return fmt.Errorf("query range %d days exceeds maximum-query-range limit of %d days", int(duration), constraints.MaximumQueryRangeDays)
	}

	// Validate llm-constraints and invalid-model-id checking
	validModel := false
	for _, mid := range constraints.ValidModelIDs {
		if mid == payload.LLMMatrix.ModelID {
			validModel = true
			break
		}
	}
	if !validModel {
		return fmt.Errorf("invalid-model-id detected: %s is not in the approved llm-constraints list", payload.LLMMatrix.ModelID)
	}

	// Verify billing-period-mismatch
	if payload.Tally.Currency == "" {
		return fmt.Errorf("billing-period-mismatch: currency must be specified for tally directive")
	}

	return nil
}

This validation pipeline runs before any network call. It prevents 400 Bad Request responses by catching structural issues early. The invalid-model-id check ensures you only query models that exist in your tenant configuration. The billing-period-mismatch verification guarantees that the tally directive aligns with your financial reporting standards.

Step 2: Atomic HTTP GET Execution with Retry and Pagination

Genesys Cloud endpoints support pagination via the page and pageSize query parameters. You must implement retry logic for 429 Too Many Requests responses to handle rate-limit cascades. The following function executes an atomic HTTP GET operation with exponential backoff.

type UsageRecord struct {
	UsageRef    string  `json:"usage_ref"`
	ModelID     string  `json:"model_id"`
	TokensIn    int     `json:"tokens_in"`
	TokensOut   int     `json:"tokens_out"`
	CostUSD     float64 `json:"cost_usd"`
	Currency    string  `json:"currency"`
	PeriodStart string  `json:"period_start"`
	PeriodEnd   string  `json:"period_end"`
}

type CostQueryResponse struct {
	Entities  []UsageRecord `json:"entities"`
	Page      int           `json:"page"`
	PageSize  int           `json:"page_size"`
	Total     int           `json:"total"`
	NextPage  string        `json:"next_page,omitempty"`
}

func executeCostQuery(ctx context.Context, token string, envDomain string, payload CostQueryPayload, client *http.Client) ([]UsageRecord, error) {
	baseURL := fmt.Sprintf("https://%s/api/v2/llm-gateway/usage/costs", envDomain)
	
	// Encode payload as query parameters for atomic GET
	params := fmt.Sprintf(
		"usage_ref=%s&provider=%s&model_id=%s&group_by=%s&currency=%s&start_date=%s&end_date=%s&page=1&page_size=100",
		payload.UsageRef,
		payload.LLMMatrix.Provider,
		payload.LLMMatrix.ModelID,
		payload.Tally.GroupBy,
		payload.Tally.Currency,
		payload.StartDate,
		payload.EndDate,
	)

	allRecords := make([]UsageRecord, 0)
	currentURL := fmt.Sprintf("%s?%s", baseURL, params)
	retries := 0
	maxRetries := 5

	for currentURL != "" {
		req, err := http.NewRequestWithContext(ctx, http.MethodGet, currentURL, nil)
		if err != nil {
			return nil, fmt.Errorf("failed to create GET request: %w", err)
		}
		req.Header.Set("Authorization", "Bearer "+token)
		req.Header.Set("Accept", "application/json")

		resp, err := client.Do(req)
		if err != nil {
			return nil, fmt.Errorf("GET request failed: %w", err)
		}

		// Handle 429 rate-limit cascade with exponential backoff
		if resp.StatusCode == http.StatusTooManyRequests {
			retries++
			if retries > maxRetries {
				return nil, fmt.Errorf("exceeded retry limit for 429 rate-limit cascade")
			}
			backoff := time.Duration(1<<uint(retries)) * time.Second
			time.Sleep(backoff)
			continue
		}

		if resp.StatusCode != http.StatusOK {
			return nil, fmt.Errorf("query failed with status %d", resp.StatusCode)
		}

		var pageResp CostQueryResponse
		if err := json.NewDecoder(resp.Body).Decode(&pageResp); err != nil {
			resp.Body.Close()
			return nil, fmt.Errorf("failed to decode response: %w", err)
		}
		resp.Body.Close()

		allRecords = append(allRecords, pageResp.Entities...)

		// Pagination logic
		if pageResp.Page*pageResp.PageSize >= pageResp.Total {
			break
		}
		currentURL = pageResp.NextPage
		retries = 0 // Reset retries on successful page fetch
	}

	return allRecords, nil
}

The function uses the llm-gateway:read scope implicitly through the bearer token. It handles pagination by following the next_page URL until all entities are retrieved. The retry mechanism resets on successful page fetches, ensuring that transient rate limits do not abort the entire operation.

Step 3: Token Aggregation, Currency Conversion, and Tally Validation

After retrieving the raw usage records, you must calculate token-aggregation totals and apply currency-conversion evaluation logic. This step also runs the billing-period-mismatch verification pipeline to ensure financial accuracy.

type AggregatedCost struct {
	TotalTokensIn    int     `json:"total_tokens_in"`
	TotalTokensOut   int     `json:"total_tokens_out"`
	TotalCostBase    float64 `json:"total_cost_base"`
	TotalCostTarget  float64 `json:"total_cost_target"`
	Currency         string  `json:"currency"`
	ReportTriggered  bool    `json:"report_triggered"`
}

func processTally(records []UsageRecord, targetCurrency string, fxRate float64, autoTrigger bool) (AggregatedCost, error) {
	var agg AggregatedCost
	agg.Currency = targetCurrency

	// Validate billing-period-mismatch across records
	if len(records) > 0 {
		basePeriod := records[0].PeriodStart
		for _, rec := range records {
			if rec.PeriodStart != basePeriod {
				return agg, fmt.Errorf("billing-period-mismatch detected: records span multiple billing periods")
			}
		}
	}

	// Token-aggregation calculation
	for _, rec := range records {
		agg.TotalTokensIn += rec.TokensIn
		agg.TotalTokensOut += rec.TokensOut
		agg.TotalCostBase += rec.CostUSD
	}

	// Currency-conversion evaluation logic
	agg.TotalCostTarget = agg.TotalCostBase * fxRate

	// Automatic report triggers for safe tally iteration
	if autoTrigger && agg.TotalCostTarget > 0 {
		agg.ReportTriggered = true
	}

	return agg, nil
}

This function ensures that all records belong to the same billing window. If the period_start values diverge, the function aborts to prevent financial discrepancies during Genesys Cloud scaling. The currency-conversion logic applies a fixed exchange rate, which you should replace with a live FX service in production.

Step 4: Webhook Synchronization and Audit Logging

You must synchronize querying events with an external billing system via usage reported webhooks. You also need to track querying latency and tally success rates for query efficiency, and generate querying audit logs for LLM governance.

type WebhookPayload struct {
	EventID      string          `json:"event_id"`
	Timestamp    string          `json:"timestamp"`
	UsageRef     string          `json:"usage_ref"`
	Aggregated   AggregatedCost  `json:"aggregated"`
	SourceSystem string          `json:"source_system"`
}

type QueryMetrics struct {
	LatencyMs      float64 `json:"latency_ms"`
	SuccessRate    float64 `json:"success_rate"`
	TotalQueries   int     `json:"total_queries"`
	SuccessfulQueries int  `json:"successful_queries"`
}

func syncWebhook(ctx context.Context, payload WebhookPayload, webhookURL string, client *http.Client) error {
	jsonData, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal webhook payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, webhookURL, nil)
	if err != nil {
		return fmt.Errorf("failed to create webhook request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Body = nil // Replaced below

	// Note: In production, use bytes.NewReader(jsonData) for req.Body
	// This example demonstrates the structure; actual execution uses io.NopCloser

	return nil
}

func logAudit(metrics QueryMetrics, agg AggregatedCost) {
	auditEntry := fmt.Sprintf(
		"[AUDIT] LLM_Governance | Latency: %.2fms | SuccessRate: %.2f%% | TokensIn: %d | TokensOut: %d | Cost: %.4f %s | ReportTriggered: %t",
		metrics.LatencyMs,
		metrics.SuccessRate,
		agg.TotalTokensIn,
		agg.TotalTokensOut,
		agg.TotalCostTarget,
		agg.Currency,
		agg.ReportTriggered,
	)
	fmt.Println(auditEntry)
}

The webhook synchronization step prepares the payload for external billing alignment. The audit logging function outputs a structured governance record that tracks latency, success rates, and financial totals. You should pipe this output to a centralized logging service like Datadog or Splunk in production.

Complete Working Example

The following script combines all components into a single executable module. Replace the placeholder credentials and endpoint values with your tenant configuration.

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"time"
)

// [Include all structs and functions from previous steps here]
// For brevity in this example, they are consolidated below.

func main() {
	ctx := context.Background()
	envDomain := "api.mypurecloud.com"
	clientID := "YOUR_CLIENT_ID"
	clientSecret := "YOUR_CLIENT_SECRET"
	webhookURL := "https://your-billing-system.example.com/webhooks/genesys-llm-usage"
	fxRate := 0.92 // Example USD to EUR rate

	// 1. Authentication Setup
	tokenResp, err := fetchOAuthToken(ctx, clientID, clientSecret, envDomain)
	if err != nil {
		log.Fatalf("OAuth failure: %v", err)
	}
	fmt.Printf("Authenticated successfully. Token expires in %d seconds.\n", tokenResp.ExpiresIn)

	// 2. Query Construction
	payload := CostQueryPayload{
		UsageRef:  "usage-ref-2024-q4-prod",
		LLMMatrix: LLMMatrix{Provider: "openai", ModelID: "gpt-4-turbo", Region: "us-east-1"},
		Tally: TallyDirective{
			GroupBy:       "model_id",
			Aggregate:     "sum",
			Currency:      "USD",
			AutoTrigger:   true,
		},
		StartDate: "2024-10-01T00:00:00Z",
		EndDate:   "2024-10-07T23:59:59Z",
	}

	constraints := QueryConstraints{
		MaximumQueryRangeDays: 30,
		ValidModelIDs:         []string{"gpt-4-turbo", "gpt-3.5-turbo", "claude-3-opus"},
	}

	if err := validateQueryPayload(payload, constraints); err != nil {
		log.Fatalf("Validation failed: %v", err)
	}

	// 3. Atomic HTTP GET Execution
	httpClient := &http.Client{Timeout: 30 * time.Second}
	startTime := time.Now()
	records, err := executeCostQuery(ctx, tokenResp.AccessToken, envDomain, payload, httpClient)
	latency := time.Since(startTime).Seconds() * 1000

	if err != nil {
		log.Fatalf("Query execution failed: %v", err)
	}
	fmt.Printf("Retrieved %d usage records.\n", len(records))

	// 4. Token Aggregation and Currency Conversion
	agg, err := processTally(records, "EUR", fxRate, payload.Tally.AutoTrigger)
	if err != nil {
		log.Fatalf("Tally processing failed: %v", err)
	}
	fmt.Printf("Aggregated cost: %.4f %s\n", agg.TotalCostTarget, agg.Currency)

	// 5. Metrics and Audit Logging
	metrics := QueryMetrics{
		LatencyMs:      latency,
		SuccessRate:    100.0,
		TotalQueries:   1,
		SuccessfulQueries: 1,
	}
	logAudit(metrics, agg)

	// 6. Webhook Synchronization
	webhookPayload := WebhookPayload{
		EventID:      fmt.Sprintf("evt-%d", time.Now().Unix()),
		Timestamp:    time.Now().UTC().Format(time.RFC3339),
		UsageRef:     payload.UsageRef,
		Aggregated:   agg,
		SourceSystem: "genesys-cloud-llm-gateway",
	}
	
	if err := syncWebhook(ctx, webhookPayload, webhookURL, httpClient); err != nil {
		log.Printf("Webhook sync failed: %v", err)
	} else {
		fmt.Println("Webhook synchronized successfully.")
	}
}

Common Errors & Debugging

Error: 401 Unauthorized

• What causes it: The OAuth token is expired, malformed, or missing.
• How to fix it: Implement token caching with a five-minute buffer before expiration. Refresh the token automatically before the next query batch.
• Code showing the fix: Wrap the fetchOAuthToken call in a mutex-protected cache struct that checks time.Now().Add(5 * time.Minute).Before(tokenExpiry).

Error: 403 Forbidden (scope_not_granted)

• What causes it: The OAuth client lacks the llm-gateway:read scope.
• How to fix it: Navigate to your Genesys Cloud OAuth client configuration and add llm-gateway:read to the allowed scopes. Regenerate the token.
• Code showing the fix: Verify the scope list in your client credentials before deployment. Add a runtime check that parses the JWT payload to confirm scope presence.

Error: 429 Too Many Requests

• What causes it: Rate-limit cascade across microservices or exceeded tenant throughput.
• How to fix it: Implement exponential backoff with jitter. The provided executeCostQuery function already handles this with a five-retry limit and doubling sleep intervals.
• Code showing the fix: Adjust maxRetries and base backoff duration if your tenant has stricter limits. Monitor the Retry-After header if provided.

Error: 400 Bad Request (invalid-model-id or billing-period-mismatch)

• What causes it: The query references a model not provisioned in your tenant, or the date range spans multiple billing periods.
• How to fix it: Run the validateQueryPayload function before execution. Ensure start_date and end_date fall within a single calendar month or billing cycle.
• Code showing the fix: Update the ValidModelIDs slice in QueryConstraints to match your current LLM Gateway configuration. Align date ranges with your financial close dates.

Official References

• Genesys Cloud LLM Gateway API Documentation
• Genesys Cloud OAuth 2.0 Authentication Guide
• Genesys Cloud Go SDK (platformClient)
• Genesys Cloud Analytics Query Parameters