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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8b4db15567bf18dcb22bf5a741ff335102b17cbbc5def8ce1d2cbfd82dc77ea' 
  AND token = 'SSCKy1xRQkb/oW/z4uRB9z7oPotFVvQDRlK0s5CbBoI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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