2. First attempt: one contract

The obvious design

A poll needs to:

1. Accept a Vote message from any wallet
2. Check whether that wallet has voted before
3. If not, count the vote and record the wallet

The first instinct is to keep everything in one contract, using a dictionary (hashmap) stored in the contract's persistent data:

struct PollStorage {
    owner:    address
    option0:  uint32
    option1:  uint32
    voters:   map<address, bool>
}

On each Vote, look up the sender in the map. If absent, add them and increment the count:

var storage = lazy PollStorage.load();
assert (msg.option == 0 || msg.option == 1) throw Errors.InvalidOption;

val alreadyVoted = storage.voters.exists(in.senderAddress);
assert (!alreadyVoted) throw Errors.AlreadyVoted;

storage.voters.set(in.senderAddress, true);
if (msg.option == 0) {
    storage.option0 += 1;
} else {
    storage.option1 += 1;
}
storage.save();

With a small number of voters it works correctly.

The wall

TON contracts store persistent data in a cell tree. A single cell holds at most 1023 bits and up to 4 references. The full tree must fit in the TVM stack when the contract runs. One address → bool entry per voter fills up that tree long before a popular poll ends.

More fundamentally: TON itself shards. Different contracts run in parallel on different shards. A single contract holding all voter state becomes a sequential bottleneck — every vote is a write to the same storage.

The target architecture

The canonical solution on TON is per-user contracts. Instead of one large map, deploy a tiny Voter contract per wallet address. The parent Poll counts votes — it never stores who voted. Each Voter tracks whether its owner has already voted. This pattern is called sharding and appears everywhere on TON — Jetton wallets, NFT items, and more.

• Poll holds two counters only: option0 and option1
• On each Vote, Poll deploys or messages a Voter contract at the deterministic address derived from the sender's wallet
• Voter rejects duplicate votes by throwing an error, which bounces the message back to Poll
• Poll's onBouncedMessage reverts the count increment

The next two pages implement this: first the contracts, then the tests that prove it works.