SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac6879494a216600f9921abe50c4165da261f9f97746641ec7d98a3119829baa' 
  AND token = 'SwY5+scFNQa7qhcQfj8RZc9w/ciN7cDRomDp58B8nXo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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