SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ad0888997f935a8b27867643791b498c82f1c18cc0ded89d79729eac4293726' 
  AND token = 'nA71pi2GZ8xDnsa+hGjU0WyBZ6QK2bvJthrOhIoQC1E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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