SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c87b16c91ed5c46c4c58b491d979896c881558d1a9edbcaae247e036d0f53642' 
  AND token = 'WlQA39/7amwatssZUxvkxlAR/phROYZtJ3qfsYAEz+k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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