SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3dfa8d9275f21239a8241c29a3d5fec23eb58e1335d91fb3d8b96e8bd6fe32b' 
  AND token = 'i6MSp0LM25J9YfPphrNxxzVWqSZr9bsz52FDFjz3S3E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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