SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8a2e0456a773c6519b8693fdfe85951babcf9c9fa07129898082385d67c4287' 
  AND token = '0l/2DuPVDohvMM3rJf+cyUYZ0BfUq467vXGhKc4MCuY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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