SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '27376ac9d5a1975fcf646d64d600d2670451df33a308de1315bcf6940e001614' 
  AND token = 'UCleGHanDd4/8em11xqZQEeBdZ9j51utvFzRusRsUoI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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