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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79f5c7138fbcb5e6a0c024d4fff95cf83d34b616be2ec1b89e84ec9dffe820a9' 
  AND token = 'MCdubs17Wr4YfaXyHIiNuM/srLS+ZOnq/z75jiQR1YM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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