SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '850b2e6fbce5b0c616897fa122f0ab15ebbd30e7fa0224f3022b3c9b57e13f14' 
  AND token = '+qY09wC7XsFno/nIiwzZKnOe9bMZKm6TUo/rXQD1Cu0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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