SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c1e103768e82ee086af0e24137fbdb280d09d5adb8fd42f078c83d99637b30c' 
  AND token = 'xDjHZRpgOYm3r+GHvnpiZsUwGH+nyM/ARq3uIzrUyWQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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