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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a689f4b87c5b96f44f9f6cc24ee6077248faf6ff5b1dc395be2f15aa19691652' 
  AND token = 'bHKEGWKxsed7VfNvCmZ6RWtYrVG+1YXGAUrh+Sowa7c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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