SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3103ea3aab57262967b5b32f657c49334827b21a39632d8df1bafe9319a4b013' 
  AND token = 'ch+sL23iet8AITsSLgoSScOF9jDH3up0TCHOrRCtjKE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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