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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b6a54ac815679c796c8cb8253629e164a89fcfe55474fbb7f72c924775088975' 
  AND token = 'OaDMbKfy8n2rrC0fiZilD90KduD7eVDGCUhHKaX3kdI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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