SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '004dcbdfb2aaee0e13739112764ebebe07a2bafc00666407ef0ff43bc137e408' 
  AND token = 'OPxHEWZ9WCVor2NKhnGKxmDuAm3F7aATYQVqwq36mDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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