SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8639966743beeae3b20caf6cc7bb5854b91a0d19f442e4bc14e6e102da915a81' 
  AND token = '+Zj0Ph+Z7/s1oGCSpFOCgPKRStpe9q7xQeHmFVsdqIA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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