SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c68b44a53c6a146475bf018413ac2bb8642368f18e5f3778874303a24c8556e5' 
  AND token = 'LegUns9+kRJZ/vFKATVbPgEHUdqX8EKqmB3KjbgUHCE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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