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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c1862dc5e9e7485e71d8d77a536b872960b37f3bd2a038cedd47ec6814da811c' 
  AND token = 'UknJHADv05zDB6QsyxQgLLwIbN8I7TH+Q4Iy+uxZ4+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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