SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6c415655d6b3827223b8f94dbf527217320f67b988ebaf9e7f205a29c7a0e16' 
  AND token = 'a3kuHq+EcBgvMNQBVoScn6L3ZT4r4z0qH4T/ug9Z6Xo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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