SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a312a56502d064750be8954a56a48645cd4a0ccdc9af07a433fd23df61b81475' 
  AND token = 'Rz08K3Gf2rNxlgkLAHBSJ/3RmentBSXuUyqn+XMjDno=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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