SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31801123fbba627ef0c5d411f7c016f6ff725694b861489290acde431a84a11e' 
  AND token = 'a3EONfppn7iUaZszNohsasbLI44gxL9aFiJTfPFCirw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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