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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b2ac01541e459171b2d97c75e4f54a8976a2e044f83d5ebe4dc217444295a309' 
  AND token = 'lrqjCFWS0DY/dMnzykBW82Sp3CspErEcodqLhsp7wRU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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