SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78abd8a60c40b6ca07dfdd878801a64e568d9e355152677fe92991ef8070429a' 
  AND token = '9dH6Pd1uTRX4sUDsZqGeM8wrz0w4nJQDw7BmaRBsOb4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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