SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd951cbea88177f2e3ed00e24d2c2e7656e176601d9bd80de8ed62659a947e02a' 
  AND token = 'fYxaYQ+kyU0L0Y+KLGCSW4hO8SDvDTffqyOKIOtFozk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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