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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'c21ec16d9b0d67b3c4e8034a5b572f0fe274ddede947b44173a5114083775f0f' 
  AND token = '3Jf7qdPZD/DkBHIocF4MHcFXHlOJGlJMMwmiONhFiSg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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