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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e0c485a19993266524e1e389b304f1a4a50432f8c9fb4ddc2b9471e51fe2f356' 
  AND token = '3tngxIiVTh3+7SSoM0mXNXLlAmtcZxJYyuMFd0uV2h0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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