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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c51699239956570b1d7c202821a7270a36ff9bcabb5bf1aa2539c11a5f5b027f' 
  AND token = 'rb1VsSBH7EEhPQC0D9B+JSe6zrwYOxt4VX65BP8Rr5c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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