SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db4aecf99ecac5944f7b57f8c571131fad1482527fa154017792b016228be547' 
  AND token = 'Nc6/uVMDTcB3ZcUdvyXmLf7+RKmA15n+gfohI+/zuGA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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