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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '40414d25edffc1d0bd9c83e51fe60c36dd0675b5baacbe7931179317b99b1fe1' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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