SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76c78ed0f52979b6a2a99e27e8fd4ef404f0fa539df972474e9c43ebb13abf28' 
  AND token = '3EafQVYocvMFpEONyiOf545W4A+VnrwsBYAWA5/8HsM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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