SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '03b6a518302d1e4ceeff556c09f832f83cc1d94db6b36e450e5f2a322f7f7604' 
  AND token = 'RtEp53BQ81jVWohXG5OjkfnPmKC7JZgv29WqQgi+tB0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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