SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8868340334be9a4693f62c33bcaa256467a026d967caf58a220fe82389df184' 
  AND token = '7G1wKu+MrcbDIjASVPSIW6Cj8UU9UtBc5KSz4dyxLd0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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