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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c41fd4e34b9cf03d9e5700777fd10bcde77dac9de7ac41f6650e40be03d0eadd' 
  AND token = 'T+kyF2P/SPyMd//VHDqWdDbrkOuFLXe5Jp3DkZwUpMo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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