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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '591c670c3a42d47cea6ca9839d7bd4d4cfa92bbea49c79074ce387eb8dddca14' 
  AND token = 'RFD3KnNAPIxFl95hF+Eume78V1KSGJ5VFTGtFctFiNk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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