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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '78200cf46006655a5df90dddb0eb8f763f8592631beda3beedf2015402935a73' 
  AND token = 'QRSpQ/209ycEbXK+tQUA2D+jfP+rUsiq2i9RMLqg+Qo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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