SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4fbcb165926a305a1090b28894c7889713ffc50adbf7313a807adba72f69d6e8' 
  AND token = '5lNJGtlhvwqzQZRfdzxqTpLXww25xDqT75tLYIg4CoY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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