SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81f4a8a49a27db1c668579075ae73528412d11e018f24be0a9e08219d3110af3' 
  AND token = 'mvbj+HP19rKLn1Yq2nwQLsk0qKfB6Zw4mHsVUWvi2IA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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