SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a573cc2aa520ea93f9650111fe97f314c342e40f244e1c460a2134510090441e' 
  AND token = 'a9+GojpcjotoTanWr4Vv4KcjcdFuKEt9gOvChhBT2iY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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