SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '338df4a3abeca046c80a2726792579f0cf25e51f8ab87ad17428c59ee40a8285' 
  AND token = 'VOB3R35UVH7VvsgH5YIFUEGbkmw6teBEBCVnBsNQty0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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