All on Telegram
Record expenses and check balances in Telegram, without another app to download.
TakoSplit / Backend engineering
Building TakoSplit
Shared expenses. Exact settlements.
TakoSplit brings shared expenses and trip settlements into Telegram. I built it around a simple idea: the group chat is already there, so splitting the bills should fit into it.
- Python
- FastAPI
- PostgreSQL
- Google Cloud Run
TAKOSPLIT / TELEGRAMLive product
TakoSplit
Chat-native expense ledger
Illustrative Telegram conversation
THE DECISIONS BEHIND THE BUILDEXPLORE THE PROJECT ↓
- Project
- Telegram bot + backend
- Core challenge
- Accurate shared expenses
- Deployment
- Cloud Run + Neon
- Payment handoff
- Optional private PayNow QR
01 / Why Telegram
The trip already has a group chat.
The starting point was simple: a lot of people already use Telegram, and the trip conversation is often there too. I didn't want to ask everyone to download another app just to keep track of shared bills.
Why I chose Telegram
I chose Telegram so the group could plan the trip and track its costs in one place. Using a familiar chat kept the setup simple: no extra app to install, and no separate place to check the bills.
Key features
Group or private trips
Use an existing group, or start a private trip with the bot and invite others.
Equal or custom splits
Share a bill evenly or enter a different amount for each person.
Running trip summaries
Keep track of shared expenses and each person's share as the trip goes on.
Simplified settlements
Turn the trip's bills into a clear plan of who pays whom.
Private PayNow QR
Get an optional exact-amount QR privately, then complete payment in your banking app.
02 / The architecture
A light interface, with the backend doing the work.
I chose Python and FastAPI for the backend, with PostgreSQL for saved trip records. Telegram handles the conversation, while the backend takes care of calculations, confirmations, and the shared expense history.
HOW IT FITS TOGETHERA HIGH-LEVEL VIEW
- Telegram
The conversation
Commands & buttons - FastAPI
The connection
Receives updates - Expense engine
The decisions
Splits & settlements - PostgreSQL
The shared record
Saved trip history
↳ A saved expense becomes a clear reply in the chat.
Cloud Run
The containerized backend runs as a hosted service.
Neon
Hosted PostgreSQL keeps trip state available across service restarts.
03 / How it connects
One trip, connected records.
A trip brings together the people, the bills, and each person's share. Keeping the original expenses separate from the final settlement makes the result easier to understand and revisit.
THE SHARED CONTEXT
A shared trip
One connected picture
participation
People
Who is part of the trip
the original bills
Expenses
Who paid, and who shared it
calculated from bills
Balances
What each person owes or gets back
the next action
Settlement
A plan for who pays whom
04 / Getting the money right
Even the extra cent needs to go somewhere.
Splitting a bill gets less straightforward when the amount does not divide evenly. I used integer cents so the shares always add up, including when someone enters custom amounts or edits a bill later.
The rounding problem
S$10.00, shared three ways
The remaining cent goes to a predictable share, keeping the total intact.
- Alex · payer
- S$3.34
- James
- S$3.33
- Sam
- S$3.33
- Total allocated
- S$10.00
Custom splits
Everyone's entered amount must reconcile with the bill.
Expense edits
Participants and their proportions stay intact when an amount changes.
05 / Reliable confirmations
The second tap matters, too.
A slow response can make someone press confirm again. Confirmation handling is idempotent, so repeating that action does not create another expense.
First confirmation
Repeated confirmation
One saved expense
Review before saving
There is a chance to check the amount and participants before confirming.
Keep the work saved
In-progress selections are saved so they can survive a service restart.
06 / Simplifying settlement
From a pile of bills to a payment plan.
At the end of a trip, each person's spending and shares are brought together into a net balance. The settlement plan simplifies who pays whom, while the original obligations remain visible to explain the result.
Before · 4 obligations
- James owes Alex S$8.33
- Sam owes Alex S$8.33
- Alex owes James S$3.00
- Alex owes Sam S$10.00
After · 2 transfers
PAYSJames
TO AlexS$3.66
TO SamS$1.67
The completed plan is saved so participants can come back to it later. The bot proposes the transfers; people make the payments themselves.
07 / Privacy by design
Shared expenses, private payment details.
Trips can start in a Telegram group or in a private chat with the bot, with invite links for others to join. Whichever way the trip runs, PayNow setup and QR delivery stay in private chats, and stored mobile numbers are encrypted.
GROUP WORKFLOW
In a group chat
- Start a shared trip
- Record group expenses
- View the running summary
- See the settlement plan
PRIVATE WORKFLOW
In a private chat
- Start a private trip
- Invite participants by link
- Add expenses and view settlement
- Set up PayNow and request QR
An optional payment handoff
The person who needs to pay can receive an exact-amount QR privately, check the recipient, and complete the transfer in their banking app.
Private delivery requires the participant to have opened a chat with the bot first.
08 / Checks & operations
Checking the details that are easy to miss.
The tests focus on money calculations, payment-detail validation, and QR generation. Running the bot also means looking after the service and the lifecycle of older trip records.
Amounts add up
Coverage includes rounding, custom splits, and edits that preserve the total.
Details stay protected
Checks cover number validation, encrypted storage, and masked display.
QRs carry the right amount
Tests check the generated image and the payment amount in its payload.
Service operations
A health check and secret redaction support running the backend.
Trip retention
Scheduled cleanup removes older completed trips so those records do not accumulate indefinitely.