SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b51a18e78a7e9b16542868ea42b8136ed322317a9eefb644e4876710c3afee25' 
  AND token = 'LveVjRBOXho+FDRdfNW1z+hgdhV36mqGzOQQZsyxcgs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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