SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8f4c4b7e9c5159625f769d651b56e1cdeafef94693aadb8ccdb903c97f0a903' 
  AND token = '8SM7ZmkwSBZI6DGgVxHhIpgMmV77Qavr+PFjeSPOVUs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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