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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5c66a5d72b216e1f3f202b52a7668d83f3b9aac6a43ee090fb38041c0a2bd91' 
  AND token = 'j0kiW8RzJGumYM3GijPfs4cwsjbhOjXS2svq21JeKVs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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