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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8268fc3838759f364a5a4230943995a5b129d708ceee045b67b5d306f1fe4d3' 
  AND token = 'D4rLT8k1rz1fFi3vdH/p8l3hto3GBk62qCHEflxMi7k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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