SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '321df25a55a93661316ee7bf50178467f166d39363d4ddc8518b7e29bd424df0' 
  AND token = 'Nw6KM7kHACiYmMNcl0NcEJN2jEhSFGs5jVSWLUY+vLU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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