https://maciejlewandowski.dev/ Field notes from custody and wallet infrastructure: Bitcoin, EVM, Solana, and the backend systems that hold real money. en https://maciejlewandowski.dev/blog/point-in-time-balances/ https://maciejlewandowski.dev/blog/point-in-time-balances/ Wed, 12 Aug 2026 12:00:00 GMT Chains never close, so a point-in-time balance has to be derived, not queried. The anchor problem, the per-chain traps, and why reproducibility is the real requirement. https://maciejlewandowski.dev/blog/rust-money-types/ https://maciejlewandowski.dev/blog/rust-money-types/ Sat, 25 Jul 2026 12:00:00 GMT Newtypes, phantom-typed currencies, checked arithmetic and typestate - how much of a financial bug class the compiler can take off your hands, for zero bytes. https://maciejlewandowski.dev/blog/backtest-lies/ https://maciejlewandowski.dev/blog/backtest-lies/ Sat, 25 Jul 2026 12:00:00 GMT Look-ahead bias, survivorship, point-in-time data and overfitting - why a backtest is a replay engine, and what that demands of it. https://maciejlewandowski.dev/blog/deposit-detection/ https://maciejlewandowski.dev/blog/deposit-detection/ Wed, 22 Jul 2026 12:00:00 GMT Proxy contracts, fee-on-transfer tokens, reorgs, UTXO edge cases and Solana token accounts - and why continuous reconciliation is the only real fix. https://maciejlewandowski.dev/blog/transaction-state-machines/ https://maciejlewandowski.dev/blog/transaction-state-machines/ Wed, 22 Jul 2026 12:00:00 GMT Broadcast is not done, confirmed is not final, and retries are where money gets lost. What breaks, chain by chain. https://maciejlewandowski.dev/blog/utxo-coin-selection/ https://maciejlewandowski.dev/blog/utxo-coin-selection/ Wed, 22 Jul 2026 12:00:00 GMT Your Bitcoin balance is not a number, it is a set. Fees, dust, privacy and the concurrency problem the tutorials skip. https://maciejlewandowski.dev/blog/stuck-transactions/ https://maciejlewandowski.dev/blog/stuck-transactions/ Wed, 22 Jul 2026 12:00:00 GMT RBF, CPFP, nonce queues, expiring blockhashes and the pinning problem - a remediation playbook for transactions that will not confirm.