SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '86b3a794357cd6585951487cd3dc1a7be98fbd9ca22c0616eaeb67e3b135cfea' 
  AND token = '6zzLFImYCiLcTbi0Z8LUxuv0ZBnZkeqj34Q0ZOyZa5E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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