SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b494d346fb98aae753c7c3168979664df9330897a550303bd27021481d93be68' 
  AND token = 'l6POYAevqrwLxTJ5xTZBHROnjvZJ0QMgEuwrF8E6vMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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