SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a7121cec066f583ad527d93b94659a6e0e82d9e7d205eb6b5b1eb890ed97640' 
  AND token = 'zRq2rdfyH2hOeYOID289bE0CNALXsmwLkS1ZgepbqWI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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