SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '684cc52724f8ff0148904d08289433990703f9127a958e298f535de34e5b4a6f' 
  AND token = 'dgBcH+mjhjrk7qfGl2UJq4xq44AbAELPPdFa8flKfwY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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