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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6aa3d67519823782ebd5159928daf9692066f50dcb17cb2737bffdf6717a5021' 
  AND token = 'UrmYKKlWloWtgn1aoaTsrSDcnSA99aOlLDSeA9q8UMo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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