SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56968eb77a06aa4699ed074a60c856b75ec520763da65e5ace1aa66b8b53d413' 
  AND token = 'DQnw2Bz6S+0+uxBh3uq/Hh0A449FTNowoXDfLQ5Q8co=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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