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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '306bb6e1db0e43255237eda403b9ea12a7c86896ef4f1d8eaca75d76a748af96' 
  AND token = 'C+/yrnQrMWmdR3211rqSDJ/sX6DD3lIEZyTTdtjh+U4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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