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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a2308d7bcbcaf55a970466e309ee77018abd054e70fd4e7d3a79c10d487e46c' 
  AND token = 'JUG5xBHlUZdngPqKO+W86JpWEQmSsw7QqIAAmn8okgw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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