feat: implement horizontal scaling optimizations for authz service

- Add /health and /ready endpoints for load balancer health checks
- Replace in-memory JWT token cache with Redis for multi-replica support
- Reduce DB connection pool from 100 to 25 connections per replica
- Add distributed rate limiting (100 req/min + 20 burst) using Redis
- Implement circuit breakers for DB and Redis to prevent cascading failures

This enables the service to scale horizontally with multiple replicas
behind a load balancer without exhausting database connections or
maintaining separate token caches per instance.

redisclient/redis.go

@@ -1,17 +1,20 @@
-// pkg/redisclient/redis.go
-
 package redisclient
 
 import (
+	"authorization/helper"
 	"context"
 	"fmt"
 	"os"
+	"time"
 
 	"github.com/redis/go-redis/v9"
 )
 
 var RDB *redis.Client
 
+// RedisCircuitBreaker protects Redis operations
+var RedisCircuitBreaker *helper.CircuitBreaker
+
 func Init() {
 	redisHost := os.Getenv("REDIS_HOST")
 	if redisHost == "" {
@@ -39,9 +42,16 @@ func Init() {
 
 	RDB = redis.NewClient(opts)
 
-	// Test connection with authentication
+	// Initialize circuit breaker
+	RedisCircuitBreaker = helper.NewCircuitBreaker("redis", 5, 2*time.Second)
+
+	// Test connection with authentication using circuit breaker
 	ctx := context.Background()
-	if _, err := RDB.Ping(ctx).Result(); err != nil {
+	err := RedisCircuitBreaker.Call(func() error {
+		_, err := RDB.Ping(ctx).Result()
+		return err
+	})
+	if err != nil {
 		panic(fmt.Sprintf("Could not connect to Redis: %v", err))
 	}