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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '28eb4b0d9a7b03309b6188787051cf7bffbf736ee6c9eb22e3b37c00a1da43de' 
  AND token = 'EnDR55SQKzjoymC//AQGfElYPJZt/WUjEh2RkIeAudQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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