SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f7849a28e2e2a331a77ed274dbc57671bb9c295c1e6a0c1a43b4625a0ddd86fa' 
  AND token = 'mKQnN/rdGRFqzhJDMwqXsZyYzsKoDM60k/iB5WiUhOU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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