SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '294c700d5c550bb139716894ce79078981b2e512c1ea738257377982ab83e343' 
  AND token = 'BN5gVxjnOx66ikC0MkXRna+BaBKMlM/SpstIAUAL6Wc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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