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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef4f3da4ce429656c1c807960a85564f9285621c1493258e7fa767a3692cecc8' 
  AND token = 'tUWBGnHoI48UDZxXb322FnQpfFB7EPp7buhunRy1VVY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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