SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c98d92aec93d2f64ae50f3098e2c70020115038ca7d9a34ef5b4ad620e539438' 
  AND token = '6zBlcZfWRFsRv0/leNWh7qoSuE/1kmJPzxj3bbC9dmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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