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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50dff3edfec7c8d4ac763515e969081252280f5608beadd0ae65b2ef17a8f513' 
  AND token = '4vaigeOqNp40GJDa/cRRHijGcFpROFixm0yfA2jDD7s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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