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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '38a74a60da5f5ec7606c7d64671b2a03b8040d39381c1444320bf381d0b1c9a6' 
  AND token = '28hzCd7NCUaQjcyvZboj0OWtRfhobYEIs33/jjeVJZs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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