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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df78dbe78026a1078f8eb9e65e113585d03fee526815dbdc7a19f1cf3e19e174' 
  AND token = '2xkfJQshJgFDDICPvppOtiJhrCQiqIyIesfrQ6VEYT0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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