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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '286c8b32efba6bb22530680e5f8c15f5e1f85d94eb4e102a3fafe72deb70843d' 
  AND token = 'SRJz8poI4zrHvXau686HWwLJccwsMggMTKBt37+haJQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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