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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3947b15ccdd6da253b3df1636aeb07ec2c1ded0598cfa592b73655d453c0d95' 
  AND token = '6BTFqBVuLL7BRgFPrXt6pBb0FHFwQr5isNEMIWdjoqY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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