SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7ea942a58e95c8553be75618b594c4c6dc990e2d0655c1fa39330f81893735a2' 
  AND token = '68kxEAbP9YaDrY3IqSRAox9h5tsaTs4IIq1z3YnjrIA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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