SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f8f8231c038958a711886cd8d0ddafaddb35012676ae1f1847056fd060da1e0' 
  AND token = 'cuxqux82ub0SDGeQnZbuOmx0+BUnYyIppZPKk+GjQZI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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