A cluster's rent-exemption line, as the two coefficients of
rent(n) = base + perByte · n.
Rent exemption is affine in the account's data length by construction —
Solana charges (ACCOUNT_STORAGE_OVERHEAD + n) · lamports_per_byte_year · exemption_threshold, which is (128 + n) · 6960 on every cluster in use.
So two probes, at n = 0 and n = 1, recover the line exactly: the first
is base, and their difference is perByte. Every other size is then
arithmetic rather than another round trip, which is what makes it safe to
state the rent on 25 release rows at once.
Exact, not fitted. Nothing here approximates or interpolates; a two-point
fit of a line through integer coefficients is the line.
A cluster's rent-exemption line, as the two coefficients of
rent(n) = base + perByte · n.Rent exemption is affine in the account's data length by construction — Solana charges
(ACCOUNT_STORAGE_OVERHEAD + n) · lamports_per_byte_year · exemption_threshold, which is(128 + n) · 6960on every cluster in use. So two probes, atn = 0andn = 1, recover the line exactly: the first isbase, and their difference isperByte. Every other size is then arithmetic rather than another round trip, which is what makes it safe to state the rent on 25 release rows at once.Exact, not fitted. Nothing here approximates or interpolates; a two-point fit of a line through integer coefficients is the line.