SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b0a78caff67d98c8a01dc4b008c18fc13aee823c4001e6e8af68bdafba76f46c' 
  AND token = 'oKcgymaLq1nww/dVgUAsOfSVwCutSmbwuTCdhDMf5os=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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