SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ed68cace61eba1a7ef9b1ff0ce3340ea96e4bc22c5bc4b11abba42773fd5f81' 
  AND token = 'sndjKWSryZFzvl4E4q6ZyyrOQ7EQgZBVkIN5udmCjMg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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