SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'defd8dc320440ae2f6c60eb3379d6cda9f4cbc24ea371be2f512a88619908f87' 
  AND token = '/3nYmTy+lNeppzBKGmzjQUgEU3TZYWsz0aZlXuLN6ZQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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