SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '139caa3570ae7fafaad06afcb1758142f74d587deaf19d13b639a8d220a9ad91' 
  AND token = '5JQb4eoYixlM+IMnuX3zAsJT5m9ZqGjPPBRRdrHGE4Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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