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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3dc1355528e507f9cc4fdfa120fb794e28cbc2b6d1a95db12f8dfe829131a78' 
  AND token = 'joD7cQLOMsOOl5FJv4HW9lIHXfSo63JN/Sx9Jg1MWW0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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