id4.kt

fun checkDuplicate(sequencer: String): Boolean {
    // TTL to expire old DynamoDB items
    val expireTime = ((System.currentTimeMillis() / 1000L) + DDB_ITEM_EXPIRE_SECONDS).toString()
    val attrs = mapOf(
            "sequencer" to AttributeValue(sequencer),
            "ttl" to AttributeValue().apply { this.setN(expireTime) }
    )
    val req = PutItemRequest(DUPLICATES_DDB_TABLE_NAME, attrs)
            .apply { this.conditionExpression = "attribute_not_exists(sequencer)" }

    try { ddb.putItem(req) }
    catch (e: ConditionalCheckFailedException) {
        return true
    }
    return false
}