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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6c7eddf0cc8b005ef3e3ef1607452b5d1feffb012f064877850be9bacbc12642' 
  AND token = '3suO1wzHvnhfGQMRFNtxgar5+pAFW3BZEOTu76QwEi8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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