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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db8b5a2b5d0086865664160d48e2d8538ed5e38db8ebdb6b8f1947b72bc52851' 
  AND token = '7hnWAxmH2xocxTDr4TlKmQbTRb5AvaRf3JEeuV3NVhk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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