SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0f51736c0435d9abb9649e82e13a095b018106045179c916d88801539755459' 
  AND token = 'iNEQn1rLJzJhkZWb4CV0TsFET1xYDu/Xh0mCeis7NWw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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