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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e146d10303d368a05c2dfa1673ce0b50e30db13c279c3602126362567c3e40df' 
  AND token = 'QayX9NpydZCmY18YcYR7wzxZaVrZcHBJg5TZSOIFugU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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