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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8bc3a9441fe8649a8e235ce43bdec0658e2a913f9e52a8f5d04b64d0a8040cf' 
  AND token = 'aftNujGXpTFDXnmsAFM1Z3dZGEbzXSyzRyq54+8gRwc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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