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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd4f2d9c3213287c485a3142f72fc76a08325a4ff479ab02d10e95344b0e574db' 
  AND token = 'MFlSJRCjxF6E+fvnWTNnTy3b5VXHwAG0iZtMOk8ZsJQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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