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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '768d63f478e7d9bbe5ed4fe8c4bb9a00d85d69bdce5ba24e46a23be2e938f9aa' 
  AND token = 'kHTqoUJddXoiNx0P2GQ1FVAuq4f+fdhNcLHTjf2iulM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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