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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b68bca43bf079cd4624e08d819175b9be558c922e08508cb00e5117a59ae5e13' 
  AND token = 'nQxm1px9rqzPPwywnJW7eAWinqDbaQppHeuOluhLxpM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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