SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9d485aaa36c59da36ff19380f70c19a07bd7c7d006149a9ccfc23aeea684c51' 
  AND token = 'cM2GMx5Q0jTJHIlJMCOgbRmdqm8pOOavFHbDl2imqyE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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