SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ab516e4cc2dedfcfd296a65bb0bfb3c13bcedc1a67558d59b310bec8d6e48cb' 
  AND token = 'S3tLwI56cMIBVD1mRKXvOTgqON5uFdWTeJz5h6ZMJLg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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