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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81c35fedd3ccb307fa6d63f3c9e2bc99888aa7bca186776a5e6ae18abab3d1c8' 
  AND token = '6L/Oba5CQ9tg8Sg8BdXRES71ql278af36iriBRbd/5Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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