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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '31f739d2719be81bf444ed35f9357275247a61f2131a07d499fa5e9a693e3b4c' 
  AND token = 'c6k4pBtB/4N0Rks0zAF1wKOsdu7M2caKkXtT+/sGltk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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