SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ad1238cf754d501a530453c5940a9cf76816748ca43d28741bcd33f4a2107ce' 
  AND token = 'rnQxjMWkpApjAUHXw66MdFvjlDN4iUx8FcUZCvgDCE0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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