Implement paginated retrieval of transactions

Given a large list of transaction records (id, userId, amount, createdAt), implement APIs to return transactions in reverse chronological order with pagination. Support both offset-based and cursor-based (createdAt,id) pagination; return page data plus metadata (hasNext, nextCursor, total if offset mode). Ensure stable ordering when multiple transactions share the same timestamp, and discuss how to keep results consistent when new records arrive between requests. Provide time/space complexities and key edge cases.