SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c1d849f5727f762be81339baa165e08f21c0e8569e30816f2df7bd11820abc55' 
  AND token = '6f3uL6l/AxYqXdDqP18BmzBOJWsyLiUQO+rDlo/gm+M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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