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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8fe9d77569ee769c2ae51e9382d2051a2fd66cdcdfcc6aff47e4728ca0b7f09' 
  AND token = 'DzKY/z6yZFWyGA8WB0bcmI155MJ5goHAui2W/0F6pW0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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