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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e41782cc3b0a9f6a181c29d53007d450f9adb158967912bc81c3feda0d2b348c' 
  AND token = 'r8IOwSrw3MLukM4aEGxSchdwYVhkVIkYGD0ZtQNnlPc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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