SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '715b3c17ef4cce22dd2e8a580182c7292e1fafdf395cc79f3dd9e6a7d6c4e66c' 
  AND token = '4fMmGJ4B79fuby8kE8ck9dsfeMXyV0mgAvmHCbnsesY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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