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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ab8862874dd096456da0ac8d068a3e2a5a87195291c497f321917ede83761b85' 
  AND token = 'aEKb5RsC5etUKa2JYgSf+5SuNvZFaAOwaldYslmshyc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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