SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53494d1f9b3dc1e8a36d57ade011ab4e1c3ee914c57e02406ab5c4503afb01f7' 
  AND token = 'JByYZXtdoZvvodk9+zZ4QFlXPTIjHuWg7B9jZK0Ugiw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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