SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bff78592de2253c00a4351a8442ad09cdb5b8f7159048f7d686fd960fa4008cd' 
  AND token = 'WNIUa5Pk/+BK3YkDYKX4pBjTbEUDqVH/WzoeRWEpWqM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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