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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9a3ff9c3bb3fe68feffb15a2ae102ca2a3688af93e36232f82d3d18acb99bc96' 
  AND token = '8PVxkDjvQ7bkFeJule1PQ9eTkqHuh+QBlV+Kk4Z2x1Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}