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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '50b85cb59f54cdb5aa9cbef9317b9923843eaca1a0840e381eb256e0e506165c' 
  AND token = 'vJeV2d+5+JauMCBDrcChvBqY2HmtNjO5U4peDwpydek=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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