SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c5ea715ce8d3aeedfb896114137350fae74eb56ea08e570ec61512585396f91' 
  AND token = 'uw3BHgwZx+IjKxUoTjrGs6GRPYvuQ/0GqjvXyhUuJ8A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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