SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c31e73d355aac09f983e74dc42c5efe759a27aa57b8e449e46e4e078151a0970' 
  AND token = 'LZsjGTQ5dk9/n5J0aD73IoxyVrl/7iyZaOPTozLqB8E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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