SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0bfbd51dceb93a81805284e6727fc706a3fbdac454189bada5e7deeab789eace' 
  AND token = 'qUM4XwzOzeSdt1awngdvsbnCe+OdgpvOzn9ymKg3mYI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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