Define what the index actually represents
An indexer translates selected chain activity into records that an application can search and display. Start by listing the questions it must answer: transfers for an address, positions for an account, or the history of a specific contract. Keep that read model distinct from business decisions such as paying an invoice or granting a product entitlement. Write down which events influence each view and which confirmations permit downstream actions. This makes it possible to rebuild a display without accidentally repeating every business action that originally followed those events.
Treat the live connection as an accelerator
Geth subscriptions deliver current events and disappear when their connection closes; they do not replace historical recovery. Use live updates to reduce delay, alongside a bounded scan that resumes from durable progress. Decide how the two paths meet without creating duplicates. The saved progress should describe data committed successfully, not merely a response received from a provider. Ask a supplier to disconnect the stream during a demonstration, create test activity, and reconnect it. The missing period should be recovered through a visible process rather than left for manual database repair.
Keep enough identity to explain every record
A transaction identifier alone may not identify one application event. Design records with the network, contract, block reference, transaction, and event position needed for the supported chain. Retain the original observation separately from the current interpretation when that helps explain corrections. Define how duplicate observations are recognized and how parser versions are tracked. For a buyer, a useful acceptance question is simple: can an operator start with a row in the dashboard and trace it back to the exact chain evidence and processing version that produced it?
Plan a deliberate reorganization path
Geth can report removed logs when a chain reorganization replaces their blocks. An integration therefore needs a policy for records that no longer belong to the canonical history. Consider marking affected observations, recalculating dependent views, and replaying the replacement range. Keep irreversible business side effects behind an explicit confirmation policy and separate them from provisional displays. During design review, walk through a small replaced block sequence on paper. Identify what changes in the database, what the customer sees, and which operator alert explains the correction without disguising it as a new transaction.
Make lag and uncertainty visible
Monitor progress against an identified chain head, provider errors, unresolved ranges, and the age of the last successful update. A worker that is running can still be falling behind. Set expectations for customers when a history is incomplete: a timestamp or temporary status is more useful than silently displaying old information as current. Provide operators with bounded recovery controls, including the range to replay and the reason for doing so. Avoid an unrestricted replay button that can trigger downstream actions again without a clear preview of its effect.
Test restart behavior before measuring throughput
Use controlled fixtures to exercise repeated events, a missing range, a changed block, a provider limit, and a crash between saving records and advancing progress. Verify that a restart produces the same intended view as an uninterrupted run. Then measure throughput using the actual contracts and query patterns you expect to support. Request migration instructions and a rebuild procedure with the delivery. The strongest evidence is not a dashboard updating quickly once; it is a documented recovery that restores correct records after the conditions your operators will eventually encounter.