SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '319b788ebb65f0785716a42f5c2e54eba6d5727d13d42de1898f92a7cfbea339' 
  AND token = '5fwjtzRgbejYfuRzKkq6TMk5mIVmfTBPf7UtHiM6ENg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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