SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a3536999b69c789d4aa6462ffce16ed2c51d89f85c15704d61664675bef673b' 
  AND token = '2bDYPBpqQwOIbBvBzryN0aOBHMIb3ZPdXCYTPJK0Ntk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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