SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b4c1d04cadcb5e3dae9905a10b339f51d8c3fecde531e422d8ff12c72cc1af7' 
  AND token = '5jBBwJuZm12fpdfyK2PtwFQOQ90fnZwpPQFHIhdYVsc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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