SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '9c4b10cdb7fb9a7dd23070c1e56a0050197f6d1e16884b27354ce647eeb48fc7' 
  AND token = 'lfU+AjeiOjMX9gqP7PXmDBAp6JvckYs8gAJ5Pr1CCMY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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