SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6bf712d28e87f5fdb1afd33949370f04fa5cd4ee69dc8feb691859fe91039fac' 
  AND token = '9nvYJ/b6KbxmLfmZ0BLRqHy/Rzv4iP4fU5Yo6gYqwNs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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