SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'da0243c685947198c64c138dbc2e651424f7fe32b1080b135fe19b8a9d2aced3' 
  AND token = 'p9KsglBEHzU86rv10z+18sCXqEP+qh+vAGu5KrtCjV8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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