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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '999588da92c2511658f9bbdeaabd1d69ac83b1d21cbc4802440501d19ca7b0fc' 
  AND token = 'QBjTDON8ZL7+5I1zO8lxZ2bdCY7PG/I9X+EUD8+d7Qs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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