SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '81d837a0fb66f5d0d6d39963b762afd4db26245ffbac0d92790101d0e9a755aa' 
  AND token = '+wirDhFAI9t+zmqqXHXapS4IENzVMC66lHr/aC2sA0Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}