SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9508126838bc1f458bc0c2be4e498e0daa44c91046a0ece28aa5620c3b315b3' 
  AND token = '5HQLQ9AiezVYvEklwFtPdgJkZykBXhRY+hG7+iCu8Vo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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