SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81de2d61e0cd20c368bec3e77284a3006e9c56aebd1bbd20fa10f3f460438b19' 
  AND token = 'xkxJnNc+i7DElKBHAXOeU0U1D5ruXmanJyxiLT62KkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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