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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6c5d3d22995d1104d00e8217a62351a1f0d08e07a55d559636e4aae0c521bb9' 
  AND token = '6JuJ2M7GzginlKFNhaY2KNKIKc0d/ET7uVz6uqR3l4E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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