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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '51f8743a0d3115dd39ccd6c0e7965a71da2cc7dfc0eb940f95686a0c1ecca25c' 
  AND token = 'efIRY3EcorX0kivBnBtzS3PI6avrIZYmheiKfbbJbw0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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