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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55a559aefc10ff09611019a101c20e91f8ee1223ff39538a09d09cdb08dc6251' 
  AND token = 'rku3PoLcW/sG2xFMl5lItTyUiwdQq+jMyN7J+GReb1A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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