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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ad42e5fb9a779c5d02879e629fa4a02deb903d083358f8b9d1162d8a13176d55' 
  AND token = '6ClRZRxRwNDVCEPqL58UforHqMgM7YBUn2pE/aSHT9g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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