SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5976034033c539fe40862d7f2de63214af1fe66cfbce3e4f3b7e3f60b9e4f899' 
  AND token = 'E+MtT3GzEHGqweszL1/kkDZQmTVIvujrthZugpJs+w8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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