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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '03a52364229649a04f0ed6f916ba7e7f4f1ac71d5cab75020cd53f1d19beaa16' 
  AND token = 'g5j+s/lPLFHf3Ey+fHQjUYUP6x2c/jdnrrcoHfqSPfo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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