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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c8b855c816c63febc166f17aadd741d608e6fce6f2e3c5424e261f0fe7898628' 
  AND token = 'BljDB0o2khFE6HLdKs//3mlarwcglhgV5Z91YTs0XNI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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