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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0311d38be4051c3dead61238f612dfd1278bc39c75310d6e042c5cd68b5c105f' 
  AND token = 'br157grQKIzFLSy2BqOUAEZDAfhmkjVVqo4zTsj3/UU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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