SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '250ee3816779aba609ff984d4cddb531b869121f957a31abde3bc9a0012ececa' 
  AND token = '6+3Ux/T88qQRxk3l7jKcuQNrRvmx1Wp/I1UAiRRDaNA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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