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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8e3c5a76f0fb81e0e9510efba87c39cdeb40649a27b47147e51cf3bb3c0f1a21' 
  AND token = 'VJ23wLVLeMzEQ8jkve9BZebdjIyW7jdH+NfwDRsfgcw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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