SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7d51dddd0048e1f5a05a8d1d2d36e44fd3564228b8be36fc12aca751c253299c' 
  AND token = '6RKxyftLH6M2lvRi+k4o5uKACkrygLKQnElN6AftSxQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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