SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '28ba4b751254696d1725c097c663133483dc7257dd577112ba6c0ab7e4afd096' 
  AND token = 's4fpoJKIjvplNWlK3LYM0wPAdfxNK7uNTDN0r+8EN78=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}