SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c8dea8f50526bb875e518360b76eaa21162c2c946427d70322d22ce671047c9' 
  AND token = 'qoKqAs+Midppqeh6TtS2b8dy6t69tdcBiNjsWvfRXBg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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