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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '084d2820102ff342b2f0773f1ab3500ed490278c3d0b3bc0016a5377f1e27f6a' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00050

JSON explain

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