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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c81ed6cde94f5dfb5977b8fb71c2bc75233b9633766a6eae977ee504a87a59d4' 
  AND token = 'b6FJ1WDnasZigsLyTUN7sfJCWQKEeNMwew1FMKp2Od4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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