SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57e6ce17283585b62c44f204e1a97810d15a308e33f0950bf34af04488336617' 
  AND token = 'GUqCJHFQhkWYvYKdBGjfiAW1ynC4/fXOc8jAMMiuE18=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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