SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c78421c17e7f000a57fb5659f7d7b79d629849871707a7e77768c44125436f5d' 
  AND token = '0IIcygGc+CUQNu9ZS/McqK6nt88rjZ3wBNZBcQckHpc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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