fix: race conditions and rollovers

server/src/_luaScriptsV2/deleteFullCustomerCache/batchDeleteFullCustomerCache.lua

@@ -0,0 +1,46 @@
+--[[
+  Batch delete multiple FullCustomer caches from Redis.
+  
+  For each customer, atomically:
+  1. Checks if test guard exists (skip that customer if so)
+  2. Sets the stale-write guard key
+  3. Deletes the cache key
+
+  KEYS: none (all keys passed via ARGV to support variable number of customers)
+
+  ARGV:
+    [1] guardTimestamp - timestamp for all guards
+    [2] guardTtl - TTL in seconds for guard keys
+    [3] customersJson - JSON array of {testGuardKey, guardKey, cacheKey} objects
+
+  Returns:
+    JSON object: { deleted: number, skipped: number }
+]]
+
+local guardTimestamp = ARGV[1]
+local guardTtl = tonumber(ARGV[2])
+local customersJson = ARGV[3]
+
+local customers = cjson.decode(customersJson)
+local deleted = 0
+local skipped = 0
+
+for _, customer in ipairs(customers) do
+    local testGuardKey = customer.testGuardKey
+    local guardKey = customer.guardKey
+    local cacheKey = customer.cacheKey
+
+    -- Check test guard first
+    if redis.call("EXISTS", testGuardKey) == 1 then
+        skipped = skipped + 1
+    else
+        -- Set stale-write guard and delete cache
+        redis.call("SET", guardKey, guardTimestamp, "EX", guardTtl)
+        local wasDeleted = redis.call("DEL", cacheKey)
+        if wasDeleted > 0 then
+            deleted = deleted + 1
+        end
+    end
+end
+
+return cjson.encode({ deleted = deleted, skipped = skipped })