SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3704bd005f3ddd00ebff22518b6bbe0b8df20f088791ac12f39c8709dcee2a1' 
  AND token = 'BTm46xDkjTtvwjUTmjMC9jVjBWcEjL9sx55s19+aOiI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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