SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76c618445ef89e52e75e2d1aea1bb9b314c1ef4ad08e833a279ed0431bffabfd' 
  AND token = 'PdVELO0VwHEvtnZX+e5ePKDjArU5rXKHz/I0N6kPrDA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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