Backend: Persist transaction backfill jobs with resumable progress checkpoints

[Junirezz]

Context

transactionBackfill.ts replays Soroban contract events for a ledger range to repair indexer gaps. Jobs and progress are tracked in in-memory Map structures.

Problem / Gap

Long-running backfill jobs are lost on process restart. Operators cannot resume partially completed ledger scans or audit historical backfill runs after deploys.

Proposed approach

• Persist backfill job metadata and progress checkpoints in Prisma.
• Resume from the last completed ledger batch on restart.
• Expose job status via existing admin backfill endpoints with durable history.
• Enforce existing MAX_LEDGER_RANGE and MAX_BATCH_SIZE guards.

Acceptance criteria

• A running backfill survives restart and resumes from the last checkpoint.
• Completed and failed jobs remain queryable for at least a configurable retention window.
• Dry-run jobs are persisted separately and never mutate DB state.
• Tests cover start, mid-run restart simulation, completion, and failure paths.

Files/areas affected

• backend/src/transactionBackfill.ts
• backend/src/eventPollingService.ts
• backend/prisma/schema.prisma

[Osifowora]

@Osifowora has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

​Hi maintainer, I would love to work on this issue. I can get started on it right away.

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[h53566186-web]

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Pls I'll like to work on this issue

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[king-aj-the-first]

@king-aj-the-first has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hii, i'd like to work on this issue

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[Bigdaddyobamo]

@Bigdaddyobamo has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello Boss Ibimode Junior, I can persist backfill jobs and checkpoints in Prisma, resume safely after restarts, preserve the ledger-range guards, and test restart, completion, failure, and dry-run paths. Please kindly assign this to me.

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