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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8ac3d9b74ec8ea910eca78a739fe8f75e7e92cc11b122a7d690c7e2ea8d89d3' 
  AND token = '0j/HFf1QYkN02K8pYSj7dYRKlkQh36ZEwgxw3dTC8Hg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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