SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6423cfd44a2d2e578f376bc657b1809da7e386e91c7ee803b58863b05d5a3c24' 
  AND token = 'gT5wIFitQaevIXZDjiSliq9pzhwZuUhA5urB65H/p0M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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