SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '309796e07420044f3115c37fdcee988903f4bfb1cbbcb517bd57ef4fc4a75ec3' 
  AND token = 'SsK5qk7ZYuvT5L++M8dpLA+QfvpXhtQlHAZLU9Swb3c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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