SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f3c76db4f6e52f01f1ad8151bef646af59b4546c37bee75a25a7a4ccd6c10b92' 
  AND token = 'LeZq42AmfMaDMKRcCD93JdkGjDDjkY7a+2IFzGPQRyg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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