SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'def54bb0e854b3fb52d86a52a9378e3974cd9adc69762a7d4c33874011c22838' 
  AND token = 'eFNmeZzUhV5ObRTf0avpaFNiERAymqbopSNBmXxCFsY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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