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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e51373048bde0a69f97a14a779b1a92c1d1d17d329d8f34544ad1d264f752b43' 
  AND token = 'yL8E35S5Q5kjliKTCMKTPzFssstejqi0h2LrdL/qyqA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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