SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ea9d141cd2fbe1b298120341f6305a9d8594bf591dde000bca2db422c5b7f66' 
  AND token = 'QRXfhopqxbcHpVfYimk82Py+U/jiWcLEWTWfdBluN60=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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