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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '855d03fdb0f2889a03041cfb01f7ce2ec570deb09d491fc73b23546bc0b29423' 
  AND token = 'AyMX4tkqoQQrzoR+0diygLiN2p1sFSuw8FZepqAccAw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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