SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '121c5f165f5f920a431399a148d61b8d96deddd34d866c622198f9f148b3a3a5' 
  AND token = 'xJn7D/y//kGvj33u6PcD6q3CFKhnRxUQMTPiOoLVqv8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}