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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8934defbb980487cd03bb1e3838ec5119644f66fc7eae8565a1410bed3025a3' 
  AND token = 'KzdHeVzd873gjCjNxvln6vwrzmkrp6O+653r/RgCywg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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