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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '38b1b9ee0df27ad3e4645dccdc15a0cf8614c9fa6b9052f7d879e58c9bfd3f60' 
  AND token = '3GbO3QGeksPhBhZlsXeU+fbt+OIsZyxXhuh0bEkF2Uo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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