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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a6f7495d2cf18414a02f602eef8d82c8dee6622564b6c0078ac71fff2b80f38e' 
  AND token = '4/YtSHs52SmUVuJl8wOARrIALeujH0vjzPf9H0aj3xk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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