SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '54b5ef4562081ace8104b573dc3c85961da971908d135821c29723073f451b92' 
  AND token = 'mTqyeDUyOpUQeRmtuhz9d3/kulLxeqcM69eE7JLwz84=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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