SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '879d86612be77a7eb15e85f332f404375e8482ac763337c40f07478fb9e9946a' 
  AND token = '6emg8V8ZObFZKPsHXg4rbuofgfbEeihwtaemukkowR8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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