SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51e14c7d242a85adcb7b83fd5cd7fe35769ab9dfa2cf55c243f886b3b61f3d49' 
  AND token = 'WoJILaz7iP3R/9OnmhGCDcCpVBoP+qbT8gUGYRk82NE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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