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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd72c590c36d0adedc7a017d902d32c1ad9b360a7b4e11c664af28175960c027d' 
  AND token = 'WtJc4m6cmVV5GneM7iMv+0of+JjSksw7yAXtDraSHUI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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