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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c785692fde4b7ef3d9c2a3266b7a43894b35481e2dccf51dc316e9c1d3ecde6d' 
  AND token = 'RsTAo0GEf7MYgaWpSRNfIlnURra4zSQ/oEyWKkhwDJk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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