SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b38271a8971507d9090f5334698cd094eb90b13e2aad535bb57af90aa5209b78' 
  AND token = 'ADjgCsn81IXnx8JKcCoEQvMkxtA8leo2bsBTATpBBN8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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