SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3f512cae658916687f6e927bb2cf7912be489a46a3e75f41342090e9c48ef0f' 
  AND token = 'IUU8DYbc5N+mqKLvdXucXUAFQmRBTgFMIbN+hf6KvpA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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